Porous membranes and polymer blends made therefrom

Abstract

A polymer composition containing at least one high molecular weight polyethylene polymer is disclosed for producing gel extruded articles. In one embodiment, a porous membrane having an excellent balance of properties, including high porosity and high strength, is produced. On one side, a very thin membrane with high strength can be formed.

Description

[Background technology]

[0001]

[0001] Polyethylene polymers have a wide variety of uses and applications. For example, high-density polyethylene polymers are useful engineering plastics that have a unique combination of abrasion resistance, surface lubricity, chemical resistance, and impact strength. They are applied to the production of high-strength fibers for use in ropes and bulletproof molded articles, and to the production of other elongated articles such as membranes for electronic devices. However, as molecular weight increases, the fluidity of these materials in the molten state decreases, so processing by conventional techniques such as melt extrusion is not always possible.

[0002]

[0002] One alternative method for producing fibers and other elongated parts from polyethylene polymers is a gel-processing method in which the polymer is combined with a solvent. The resulting gel can be extruded to form fibers or films, which may be stretched in one or two directions as a substantial portion of the solvent is removed.

[0003]

[0003] Membranes made from polyethylene polymers via gel processing can be formed to have many beneficial properties. For example, microporous membranes 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 ion permeability due to the porous nature of the material. The ion permeability characteristics of microporous polyethylene membranes make the material particularly well suited for regulating electrochemical reactions within batteries.

[0004]

[0004] In addition to possessing the microporous properties and other physical characteristics such as chemical resistance, polyethylene membranes also offer a property known in the industry as having an effective "shutdown effect." The shutdown effect refers to the fact that when the polyethylene separator exceeds a certain temperature, the micropores within it automatically close. When the pores in the polyethylene membrane close when a certain temperature is reached, ions are unable to pass through the membrane, and the electrochemical function of the battery stops. This effect is an important safety mechanism for batteries as it prevents thermal runaway reactions from continuing and prevents the battery from overheating and creating potentially harmful conditions. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005]

[0005] In addition to chemical resistance and shutdown properties, polymer films should also have excellent mechanical properties. For example, microporous films should have relatively high puncture strength, tensile strength, and tensile modulus, especially when used as separators in battery applications. In this regard, there is always a need to improve the above film properties. The disclosure of the present invention is directed toward improving at least one of the above properties through the use of specific polymer formulations. [Means for solving the problem]

[0006]

[0006] Generally, the present disclosure is directed toward polymer compositions particularly well suited for gel processing applications for producing various articles such as fibers and membranes. The polymer compositions of the present disclosure include blends of different polymers, for example, blends of at least three different polyethylene polymers, which, when blended together, produce an excellent combination of mechanical and physical properties. For example, membranes having excellent puncture strength and / or pin strength in combination with an optimal amount of porosity can be produced according to the present disclosure.

[0007]

[0007] In one aspect, the present disclosure is directed toward porous membranes well suited for use in electronic components. For example, the membranes are particularly well suited for use as membranes in lithium-ion batteries for separating the anode from the cathode. Porous membranes fabricated according to the present disclosure may have an excellent balance of properties. For example, a porous membrane may have a tensile strength greater than about 160 MPa, e.g., greater than about 170 MPa, e.g., greater than about 180 MPa, e.g., greater than about 185 MPa, and may generally have a tensile strength of less than about 500 MPa. A porous membrane may have the above strength characteristics while maintaining a high degree of porosity. For example, a membrane may have a porosity of about 25% to about 38%. The Gurley permeability of a porous membrane may be about 110 seconds / 100cc to about 400 seconds / 100cc. In addition, the porous membrane may exhibit a puncture strength per unit weight greater than approximately 250 gf / gms, for example, greater than approximately 260 gf / gms, for example greater than approximately 270 gf / gms, for example greater than approximately 280 gf / gms, for example greater than approximately 290 gf / gms, for example greater than approximately 300 gf / gms.

[0008]

[0008] In one aspect, the porous membrane described above can be formed from one or more high molecular weight polyethylene polymers. In one embodiment, the porous membrane contains a high molecular weight polyethylene polymer having a molecular weight of about 3.1 million g / mol to about 5.2 million g / mol, for example, a high molecular weight polyethylene polymer having a molecular weight of about 3.2 million g / mol to about 4.6 million g / mol, for example, about 3.3 million g / mol to about 3.9 million g / mol. The polyethylene polymer may be present in the porous membrane in an amount of about 10 to about 35% by weight, for example, about 12 to about 25% by weight. The polyethylene polymer may be blended with other polyethylene polymers in the formation of the membrane. For example, the other polyethylene polymer may include a polyethylene polymer having a molecular weight of about 1.1 million g / mol to about 3.1 million g / mol, for example, about 1.2 million g / mol to about 2.9 million g / mol. The porous membrane may further contain another polyethylene polymer having a molecular weight of approximately 200,000 g / mol to approximately 1,100,000 g / mol, for example, approximately 300,000 g / mol to approximately 1,000,000 g / mol.

[0009]

[0009] In the above embodiment, the porous membrane may have a thickness of about 2 micrometers to about 20 micrometers, for example, about 3 micrometers to about 17 micrometers.

[0010]

[0010] In another aspect, the present disclosure is directed toward porous membranes having excellent physical properties in combination with extremely thin thicknesses. The porous membranes may be made from at least one high molecular weight polyethylene polymer and may have a thickness of less than about 6.8 micrometers, for example less than about 6.5 micrometers, for example less than about 6.2 micrometers, for example less than about 5.8 micrometers, for example less than about 5.4 micrometers, for example less than about 5.1 micrometers, for example less than about 4.9 micrometers, and may generally have a thickness greater than about 2 micrometers, for example greater than about 3 micrometers. Even with the thicknesses mentioned above, porous membranes made according to the present disclosure may exhibit a pinpoint strength greater than about 400 gf, for example greater than about 410 gf, for example greater than about 420 gf. The porous membrane may have a porosity of about 20% to about 50%, for example, about 22% to about 38%, and a Gurley permeability of about 110 seconds / 100cc to about 280 seconds / 100cc. The porous membrane may also have a basic weight of about 2.6 gsm to about 3.9 gsm. The porous membrane may also have a tensile strength greater than about 200 MPa when tested in at least one direction, for example, longitudinally or transversely, for example, greater than about 250 MPa, for example, greater than about 275 MPa.

[0011]

[0011] In yet another aspect, the present disclosure is directed toward porous membranes made from a blend of polyethylene polymers. The blend may comprise a first polyethylene polymer, a second polyethylene polymer, and a third polyethylene polymer. The first polyethylene polymer may have a molecular weight of about 200,000 g / mol to about 1,100,000 g / mol, for example, about 600,000 g / mol to about 1,000,000 g / mol, for example, about 500,000 g / mol to about 800,000 g / mol, for example, about 500,000 g / mol to about 700,000 g / mol. The first polyethylene polymer may be present in the membrane in an amount of about 3 to about 25% by weight, for example, in an amount of about 5 to about 15% by weight, for example, in an amount of about 8 to about 12% by weight.

[0012]

[0012] The second polyethylene polymer contained in the porous membrane may be present in a larger amount than the other polyethylene polymers. The second polyethylene polymer may have a molecular weight of about 1.1 million g / mol to about 3.1 million g / mol, for example, about 1.2 million g / mol to about 2.9 million g / mol, for example, about 1.5 million g / mol to about 2.5 million g / mol, or for example, about 1.8 million g / mol to about 2.2 million g / mol. The second polyethylene polymer may be present in the porous membrane in an amount of about 25% to about 85% by weight, for example, about 50% to about 85% by weight, or for example, about 65% to about 85% by weight.

[0013]

[0013] According to the present disclosure, the porous membrane further comprises a third polyethylene polymer which has been found to offer various advantages and benefits. Combinations of the third polyethylene polymer with other polymers produce polymer compositions that are easier to process than previously produced compositions and porous membranes that have enhanced strength characteristics even at thin thicknesses. The third polyethylene polymer may have a molecular weight of, for example, about 3.1 million g / mol to about 5.2 million g / mol, for example, about 3.2 million g / mol to about 4.6 million g / mol, for example, about 3.3 million g / mol to about 3.9 million g / mol, for example, about 3.3 million g / mol to about 3.8 million g / mol. The third polyethylene polymer may be present in the porous membrane in an amount of about 10 to about 35% by weight, for example, about 12 to about 30% by weight, for example, about 12 to about 25% by weight, for example, about 12 to about 20% by weight.

[0014]

[0014] A porous membrane made from the polyethylene polymer blend described above can exhibit a puncture strength greater than about 400 gf, for example greater than about 410 gf, for example greater than about 420 gf. The puncture strength per unit weight may be greater than about 250 gf / gms, for example greater than about 260 gf / gms, for example greater than about 270 gf / gms, for example greater than about 280 gf / gms, for example greater than about 290 gf / gms. The porous membrane may have a tensile strength greater than about 160 MPa in at least one direction, for example greater than about 180 MPa, for example greater than about 200 MPa, for example greater than about 220 MPa, for example greater than about 240 MPa, for example greater than about 260 MPa. The above strength characteristics can be obtained while having a relatively porous structure. For example, the porous membrane may have a porosity of approximately 28% to approximately 35% and a Guarley permeability of approximately 110 seconds / 100cc to approximately 500 seconds / 100cc.

[0015]

[0015] Other features and aspects of this disclosure will be discussed in more detail below. Brief explanation of the drawing

[0016] The present disclosure can be better understood with reference to the following drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [Figure 1] Figure 1 is a cross-sectional view of an electronic device such as a battery incorporating a porous membrane prepared in accordance with the present disclosure. [Figure 2] Figure 2 is a graphical representation of a portion of the results achieved in the examples hereinafter. [Figure 3] Figure 3 is a graphical representation of a portion of the results achieved in the examples hereinafter. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017]

[0017] Repeated use of reference signs in the present specification and drawings is intended to represent the same or similar features or elements of the present invention. definition

[0018] Pin puncture strength, as used herein, may be measured using a standardized test. One method of measuring pin puncture strength is according to ASTM test F1306 (2021). This test is capable of measuring puncture strength in addition to puncture strength versus thickness (mN / micrometer) or puncture strength per weight (gf / gms).

[0018]

[0019] Pin puncture strength may also be measured in accordance with the Chinese national standard GB / T 36363-2018. The results may be measured in gf (grams force).

[0020] Both of the above tests can be performed using an Instron 5967 Universal Testing Instrument.

[0019]

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

[0022] The density of the polymer is determined according to ISO test 1183, g / cm³. 3 It is measured in units of [unit].

[0020]

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

[0024] The average molecular weight of a polymer is determined using Margolies' formula.

[0021]

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

[0022]

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

[0023]

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

[0024] procedure: 1.1. Samples and Sample Preparation Using a sample art knife, cut each sample material into a minimum of three 60mm ± 0.5 × 60mm ± 0.5 mm samples.

[0025] 1.2. Apparatus and Measurement 3.2.1 Using an L&W micrometer, obtain five thickness readings for each 60 mm × 60 mm sample (average of five readings). Record this value as the thickness of the sample.

[0026] 3.2.2 Weigh the sample directly using a scale. Record this value as the weight of the sample. 3.2.3 Place three samples of the same material together and repeat steps 2.2.1 and 3.2.2 to obtain the bulk thickness and bulk weight.

[0027] The density is calculated to three significant figures as follows: a. Dfilm = Density (film) = Weight of sample / THK * square Dfilm = density of the sample, mg / mm³ 3 Wt = weight of the sample, mg THK = Thickness of sample, mm square = area of ​​the sample, (mm²) 2 ) b.D polymer = density (polymer) 0.95 (g / cm³) 3 ) D polymer: High density of raw materials, no pores.

[0028] c. Porosity = (1-Dfilm / Dpolymer)×100% Detailed explanation

[0028] It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit any broader aspects of the present disclosure.

[0029]

[0029] Generally, the present disclosure is directed toward a variety of extruded articles formed from polymer compositions containing at least one high molecular weight polyethylene polymer. In one aspect, the present disclosure is directed toward porous membranes particularly well suited for use as separators in electrochemical cells such as lithium-ion batteries. Porous membranes fabricated according to the present disclosure have been found to have, for example, a unique and highly beneficial blend of properties. For example, membranes can be formed that have very high strength characteristics while remaining highly porous. In one aspect, very thin membranes can be formed while having an excellent balance between strength and porosity.

[0030]

[0030] The disclosure is also directed to polymer compositions well suited for producing gel extruded articles such as fibers and films containing porous membranes. The polymer composition contains a plurality of polyethylene resins, for example, high-density polyethylene particles, combined with a plasticizer used to facilitate the formation of the article. As the article is formed, the plasticizer can be evaporated and removed, and an extruded article having improved mechanical properties can be obtained.

[0031]

[0031] To produce extruded articles according to this disclosure, various different polyethylene polymers can be selected and blended together in specific amounts or ratios. In addition, the process can be adjusted according to specific desired results. For example, in one aspect, a porous membrane made according to this disclosure can be stretched by a specific amount to obtain a desired thickness, and at the same time, the polymer chains can be oriented to improve strength.

[0032]

[0032] In one aspect, it has been found that incorporating high molecular weight polyethylene polymers having a specific molecular weight range can, unexpectedly, improve strength such as pin puncture strength and simultaneously improve the processability of the polymer composition. For example, high molecular weight polyethylene polymers may generally have a molecular weight greater than about 3.1 million g / mol and less than about 5.2 million g / mol, for example, from about 3.2 million g / mol to less than about 4.6 million g / mol, for example, less than about 3.9 million g / mol. In one aspect, the above high molecular weight polyethylene polymers can be incorporated into articles formed according to this disclosure in an amount of about 10% to about 35% by weight.

[0033]

[0033] In one aspect, a gel extruded article can be made according to the present disclosure that may contain at least two different types of polyethylene polymers, for example, at least three different types of polyethylene polymers. The polymer composition used to produce the gel extruded article may include, for example, a first polyethylene polymer having a relatively low molecular weight, a second polyethylene polymer having a medium-range molecular weight, and a third polyethylene polymer having a relatively high molecular weight. The second polyethylene polymer may be present in the composition and article in a larger amount than the first and third polyethylene polymers. The gel extruded article can be formed without containing other polyolefin polymers such as polypropylene polymer.

[0034]

[0034] Combining the first polyethylene polymer and the third polyethylene polymer with the second polyethylene polymer can bring about various advantages and benefits. For example, a porous membrane formed from a polymer combination may have improved mechanical properties. For example, compared to a membrane made from the second polyethylene polymer alone, a membrane made from a blend of three different polyethylene polymers may have an increase in pin puncture strength of about 3% or more, for example, about 5% or more, for example, about 8% or more, for example, about 12% or more, for example, about 15% or more, for example, about 18% or more, and generally less than about 80%, at the same porosity level and / or the same thickness and base weight.

[0035]

[0035] The tensile strength in the machine direction and cross-machine direction of the film made according to this disclosure can also be improved at the same porosity level and thickness compared to a film made solely from the second polyethylene polymer. For example, the tensile strength in either direction can be increased by more than about 3%, for example more than about 4%, and for example more than about 5%.

[0036]

[0036] In addition to improved mechanical properties, it has also been found that combining polyethylene with lower and higher molecular weights with polyethylene in the medium molecular weight range dramatically improves the ability of the resulting composition to be melt-processed into articles. Furthermore, the ratios and amounts of different polyethylene polymers can be adjusted and controlled to optimize one or more properties that would not be possible when producing articles from a single polyethylene polymer in the final product.

[0037]

[0037] In one embodiment, although optional, each polyethylene polymer incorporated into the polymer composition is a high-density polyethylene polymer. For example, each polyethylene polymer is approximately 0.92 g / cm³ 3 Or larger, for example, about 0.93 g / cm³ 3or greater, for example about 0.94 g / cm 3 or greater, generally about 1 g / cm 3 less than, for example about 0.97 g / cm 3 may have a density less than.

[0038]

[0038] The polyethylene polymer may be made from more than 90% of ethylene-derived units, for example more than 95% of ethylene-derived units, or may be made from 100% of ethylene-derived units. The polyethylene may be a homopolymer or a copolymer, for example a terpolymer having other monomer units.

[0039]

[0039] The first polyethylene polymer, the second polyethylene polymer, and the third polyethylene polymer each have different molecular weight ranges. In one aspect, 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 composition having an average molecular weight of at least about 3×10 5 g / mol, and as used herein, is intended to include very high molecular weight polyethylene and ultra-high molecular weight polyethylene. For the purposes of the present specification, the molecular weights referred to herein are determined according to Margolies' formula ("Margolies molecular weight").

[0040]

[0040] "Very-high molecular weight polyethylene" has a molecular weight of about 1×10 6 g / mol to about 3×10 6 g / mol refers to a polyethylene composition having a weight average molecular weight. In some embodiments, the molecular weight of the very high molecular weight polyethylene composition is about 2×106 From g / mol to approximately 3 × 10 6 It is in the range of less than g / mol.

[0041]

[0041] "Ultra-high molecular weight polyethylene" is at least about 3 × 10 6 This refers to a polyethylene composition having an average molecular weight of g / mol. In some embodiments, the molecular weight of the ultra-high molecular weight polyethylene composition is approximately 3 × 10⁻⁶. 6 g / mol ~ approx. 30×10 6 g / mol, or approximately 3 × 10⁻⁶ 6 g / mol ~ approx. 20×10 6 g / mol, or approximately 3 × 10⁻⁶ 6 g / mol ~ approx. 10×10 6 g / mol, or approximately 3 × 10⁻⁶ 6 g / mol ~ approx. 6×10 6 It is g / mol.

[0042]

[0042] In one aspect, high-density polyethylene polymer is a homopolymer of ethylene. In another embodiment, high-density polyethylene polymer may be a copolymer. For example, high-density polyethylene polymer may be a copolymer of ethylene and another olefin containing 3 to 16 carbon atoms, for example 3 to 10 carbon atoms, for example 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-methylpenta-1-ene, 1-decene, 1-dodecene, 1-hexadecene, and the like. Polyene comonomers such as 1,3-hexadiene, 1,4-hexadiene, cyclopentadiene, dicyclopentadiene, 4-vinylcyclohexa-1-ene, 1,5-cyclooctadiene, 5-vinylidene-2-norbornene, and 5-vinyl-2-norbornene are also available herein. The amount of non-ethylene monomers in one or more copolymers, if present, may be less than about 10 mol.%, e.g., less than about 5 mol.%, e.g., less than about 2.5 mol.%, e.g., less than 1 mol.%, in which case mol.% is based on the total molar amount of monomers in the polymer.

[0043]

[0043] In one embodiment, the high-density polyethylene polymer may have a unimodal 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 that has distinct higher molecular weights and distinct lower molecular weights (e.g., two distinct peaks) in the size exclusion chromatography or gel permeation chromatography curve. In another embodiment, the high-density polyethylene polymer may exhibit more than two molecular weight distribution peaks, such that polyethylene exhibits a multimodal (e.g., trimodal, tetramodal, etc.) distribution. Alternatively, the high-density polyethylene polymer may exhibit a broad molecular weight distribution, in which case the polyethylene consists of a blend of higher molecular weight components and lower molecular weight components such that the size exclusion chromatography or gel permeation chromatography curve does not show at least two distinct peaks, but instead shows one distinct peak that is broader than the peaks of the individual components.

[0044]

[0044] Any method known in the art can be used to synthesize polyethylene. Polyethylene powder is typically produced by catalytic polymerization of ethylene monomers, or optionally by catalytic polymerization with one or more other 1-olefin comonomers, where the 1-olefin content in the final polymer is less than or equal to 10% of the ethylene content, and heterogeneous catalysts and organoaluminum or magnesium compounds are used as cocatalysts. Ethylene is usually polymerized in the gas phase or slurry phase at relatively low temperatures and pressures. The polymerization reaction may be carried out at temperatures in the range of 50°C to 100°C and pressures in the range of 0.02 to 2 MPa.

[0045]

[0045] The molecular weight of polyethylene can be adjusted by adding hydrogen. In addition, temperature and / or the type and concentration of co-catalyst may be used to fine-tune the molecular weight. In addition, to avoid contamination and contamination of the product, the reaction may be carried out in the presence of an antistatic agent.

[0046]

[0046] Suitable catalyst systems include, but are not limited to, Ziegler-Natta type catalysts. Typically, Ziegler-Natta type catalysts are derived from a combination of a transition metal compound from groups 4 to 8 of the periodic table and an alkyl or hydride derivative of a metal from groups 1 to 3 of the periodic table. Commonly used transition metal derivatives include metal halides or esters or combinations thereof. Exemplary Ziegler-Natta catalysts include, but are not limited to, those based on reaction products of aluminum or magnesium alkyl and organoaluminum or magnesium compounds such as titanium, vanadium or chromium halides or esters. Heterogeneous catalysts may or may not be supported on a porous, micronized material such as silica or magnesium chloride. Such supports may be added during catalyst synthesis or may be obtained as a chemical reaction product of the catalyst synthesis itself.

[0047]

[0047] In one embodiment, a suitable catalyst system can be obtained by the reaction of a titanium(IV) compound and a trialkylaluminum compound in an inert organic solvent at a temperature in the range of -40°C to 100°C, preferably -20°C to 50°C. The concentration of the starting materials is in the range of 0.1 to 9 mol / L, preferably 0.2 to 5 mol / L, for the titanium(IV) compound, and in the range of 0.01 to 1 mol / L, preferably 0.02 to 0.2 mol / L, for the trialkylaluminum compound. The titanium component is added to the aluminum component over a period of 0.1 to 60 minutes, preferably 1 to 30 minutes, and the molar ratio of titanium to aluminum in the final mixture is in the range of 1:0.01 to 1:4.

[0048]

[0048] In another embodiment, a preferred catalyst system is obtained by a one- or two-step reaction of a titanium(IV) compound and a trialkylaluminum compound in an inert organic solvent at a temperature in the range of -40°C to 200°C, preferably -20°C to 150°C. In the first step, the titanium(IV) compound is reacted with the trialkylaluminum compound at a temperature in the range of -40°C to 100°C, preferably -20°C to 50°C, using a titanium-to-aluminum molar ratio in the range of 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 in the range of 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 to 800 minutes, preferably 30 to 600 minutes. 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 titanium-to-aluminum molar ratio in the range of 1:0.01 to 1:5.

[0049]

[0049] In yet another embodiment, a preferred catalyst system is obtained by a procedure in which, in the first reaction step, a magnesium alcoholate is reacted with titanium chloride in an inert hydrocarbon at a temperature of 50°C to 100°C. In the second reaction step, the formed reaction mixture is subjected to heat treatment at 110°C to 200°C for a period of about 10 to 100 hours, with the release of alkyl chloride, until no further alkyl chloride is released, and the solid is then removed from the soluble reaction product by washing several times with hydrocarbon.

[0050]

[0050] In further embodiments, catalysts supported on silica, such as the commercially available catalyst system Sylopol 5917, can also be used.

[0051] Using such catalytic systems, polymerization is typically carried out in a suspension, at low pressure and temperature, in one or more steps, continuously or in batches. 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 and 5 MPa. Trialkylaluminum, for example, but not limited to, isoprenylaluminum and triisobutylaluminum are used as cocatalysts such that the Al:Ti ratio (cocatalyst to 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 an inert organic solvent typically used in Ziegler-type polymerization. Examples include 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 to 50, preferably in the range of 0 to 10. The polymer is isolated and dried in a fluidized bed dryer under nitrogen. The solvent may be removed by steam distillation if a high-boiling point solvent is used. Salts of long-chain fatty acids may be added as stabilizers. Typical examples are calcium stearate, magnesium stearate, and zinc stearate.

[0051]

[0052] Other catalysts, such as Phillips catalysts, metallocenes, and post-metallocenes, may be used at the discretion of the user. Generally, co-catalysts such as almoxanes or alkylaluminum or alkylmagnesium compounds are also employed. Other suitable catalyst systems include phenolate ether ligands of group 4 metals.

[0052]

[0053] In one embodiment, one or more of the polyethylene polymers present in the polymer composition of the Disclosure have a relatively low bulk density when measured according to DIN 53466. For example, in one embodiment, the bulk density of one or more of the polyethylene polymers is generally about 0.5 g / cm³. 3It is less than, for example, about 0.4 g / cm³. 3 Less than, for example, about 0.35 g / cm³ 3 Less than, for example, about 0.33 g / cm³ 3 Less than, for example, about 0.28 g / cm³ 3 Less than, for example, about 0.26 g / cm³ 3 It is less than 0.1 g / cm³. The bulk density is generally about 0.1 g / cm³. 3 Larger, for example, about 0.15 g / cm³ 3 Larger.

[0053]

[0054] As described above, each polyethylene polymer contained in the compositions of this disclosure has a different molecular weight and, in particular, a different average molecular weight. The average molecular weight is determined according to Margolies' formula. The molecular weight can first be determined by measuring the viscosity number according to DIN EN ISO Test 1628. The flow of the dry powder is measured using a 25 mm nozzle. The molecular weight is then calculated from the viscosity number using Margolies' formula.

[0054]

[0055] The first polyethylene polymer contained in the polymer composition of this disclosure generally has a lower molecular weight than the second and third polyethylene polymers. The first polyethylene polymer may generally have a molecular weight of about 200,000 g / mol to about 1,100,000 g / mol, including all ranges in 50 g / mol increments between them, or a molecular weight of about 300,000 g / mol to about 1,000,000 g / mol, including all ranges in 50 g / mol increments between them. For example, the molecular weight may be greater than about 400,000 g / mol, for example, greater than about 500,000 g / mol, for example, greater than about 550,000 g / mol, for example, greater than about 580,000 g / mol. The molecular weight may be less than approximately 900,000 g / mol, for example less than approximately 800,000 g / mol, for example less than approximately 700,000 g / mol, for example less than approximately 650,000 g / mol.

[0055]

[0056] The amount of the first polyethylene polymer present in the polymer composition may vary depending on various factors such as the desired result. In one aspect, the first polyethylene polymer may be added to the polymer composition in an amount sufficient to improve the processing of the composition, particularly during the gel extrusion process. In one embodiment, the first polyethylene polymer is present in the polymer composition (based on the total amount of polymer present) or in any article formed from the polymer composition, in an amount greater than about 3% by weight, for example, greater than about 5% by weight, for example, greater than about 8% by weight, for example, greater than about 9% by weight, and generally in an amount less than about 25%, for example, less than about 22% by weight, for example, less than about 18% by weight, for example, less than about 15% by weight, for example, less than about 12% by weight. 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.

[0056]

[0057] The second polyethylene polymer present in the polymer composition generally has a molecular weight of approximately 1,100,000 g / mol to approximately 3,100,000 g / mol, for example, approximately 1,200,000 g / mol to approximately 2,900,000 g / mol, including all ranges between them in 50,000 g / mol increments. For example, the second polyethylene polymer may have a molecular weight greater than about 1,300,000 g / mol, for example greater than about 1,400,000 g / mol, for example greater than about 1,500,000 g / mol, for example 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 2,900,000 g / mol, for example less than about 2,500,000 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.

[0057]

[0058] The second polyethylene polymer may be present in the polymer composition or an article made from that composition in a greater amount than the first polyethylene polymer and the third polyethylene polymer. For example, the second polyethylene polymer may be the main polymer contained in the polymer composition. However, in other embodiments, the third polyethylene polymer may be present in a greater amount 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, based on the total amount of polyethylene polymer present, for example, greater than about 30% by weight, for example, greater than about 34% by weight, for example, greater than about 38% by weight, for example, greater than about 42% by weight, for example, greater than about 50% by weight, for example, greater than about 53% by weight, for example, greater than about 58% by weight, for example, greater than about 62% by weight, for example, greater than about 65% by weight, for example, greater than about 73% by weight. The second polyethylene polymer is generally present in the polymer composition or an article made from that composition in an amount of less than about 85% by weight, for example less than about 80% by weight, for example less than about 78% by weight, for example less than about 60% by weight, for example less than about 55% by weight, for example less than about 50% by weight, based on the total amount of polyethylene polymer present in the composition.

[0058]

[0059] The third polyethylene polymer with the largest molecular weight may generally have a molecular weight of approximately 3.1 million g / mol to approximately 5.2 million g / mol, for example, approximately 3.2 million g / mol to approximately 4.6 million g / mol, including all ranges between them in 50,000 g / mol increments. For example, the third polyethylene polymer may have a molecular weight greater than approximately 3,300,000 g / mol, for example greater than approximately 3,350,000 g / mol, for example greater than approximately 3,400,000 g / mol, for example greater than approximately 3,450,000 g / mol. The molecular weight of the third polyethylene polymer is generally less than approximately 4,400,000 g / mol, for example less than approximately 3,900,000 g / mol, for example less than approximately 3,800,000 g / mol, for example less than approximately 3,750,000 g / mol, for example less than approximately 3,700,000 g / mol.

[0059]

[0060] The third polyethylene polymer may be present in the polymer composition in an amount generally of about 5% to about 45% by weight, based on the total weight of polyethylene polymer present in the composition. For example, the third polyethylene polymer may be present in the polymer composition in an amount greater than about 10% by weight, for example, greater than about 12% by weight, for example, greater than about 14% by weight, for example, greater than about 18% by weight, for example, greater than about 22% by weight, for example, greater than about 25% by weight, for example, greater than about 28% by weight, for example, greater than about 30% by weight, for example, greater than about 35% by weight. The third polyethylene polymer is generally present in an amount of less than about 40% by weight, based on the total weight of polyethylene polymers present in the composition, for example, less than about 35% by weight, for example less than about 30% by weight, for example less than about 28% by weight, for example less than about 24% by weight, for example less than about 20% by weight, for example less than about 18% by weight, for example less than about 15% by weight.

[0060]

[0061] Prior to forming an article from the polymer compositions of this disclosure, each of the polyethylene polymers may exist in the form of particles. For example, in one embodiment, the polymer composition contains particles formed from a first polyethylene polymer alone, particles formed from a second polyethylene polymer alone, and particles formed from a third polyethylene polymer alone, all blended together. Alternatively, two or more of the polyethylene polymers may be blended or compounded together beforehand. 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 and third polyethylene polymers, a combination of the first and second polyethylene polymers, a combination of the first and third polyethylene polymers, or a combination of the first, second, and third polyethylene polymers.

[0061]

[0062] In one embodiment, the polyethylene particles may be a free-flowing powder. The particles may have a volume-based median particle size (d50) of less than 210 micrometers. For example, the median particle size (d50) of polyethylene particles may be less than about 170 micrometers, for example less than about 150 micrometers. The median particle size (d50) is generally greater than about 20 micrometers, for example greater than about 70 micrometers, for example greater than about 110 micrometers. The powder particle size can be measured using a laser diffraction method in accordance with ISO 13320.

[0062]

[0063] In one embodiment, 90% of the polyethylene particles may have a particle diameter of less than about 250 micrometers. In another embodiment, 90% of the polyethylene particles may have a particle diameter of less than about 200 micrometers, for example, less than about 170 micrometers.

[0063]

[0064] Each polyethylene polymer may have a viscosity number ranging from at least 100 mL / g, e.g., at least 500 mL / g, e.g., at least 700 mL / g, e.g., at least 900 mL / g, e.g., at least 1,000 mL / g, to less than about 6,000 mL / g, e.g., less than about 5,000 mL / g, e.g., less than about 4,000 mL / g, e.g., less than about 3,000 mL / g, e.g., less than about 1,8 when determined using the concentration in 0.0002 g / mL of decahydronaphthalene according to ISO 1628 Part 3.

[0064]

[0065] The high-density polyethylene polymer may have a crystallinity of at least about 40% to 85%, for example, 45% to 80%. In one aspect, the crystallinity may be greater than about 50%, for example, greater than about 55%, for example, greater than about 60%, for example, greater than about 65%, for example, greater than about 70%, and generally less than about 80%.

[0065]

[0066] In forming gel extruded articles, polyethylene particles containing at least one or at least two high molecular weight polyethylene polymers can be combined with a plasticizer to form a polymer and plasticizer composition that is well suited for producing gel extruded articles such as porous membranes. Generally, polyethylene particles are present in the polymer and plasticizer composition in an amount of up to about 50% by weight. For example, high-density polyethylene particles may be present in the polymer and plasticizer composition in an amount of less than about 45% by weight, for example, less than about 40% by weight, for example, less than about 35% by weight, for example, less than about 30% by weight, for example, less than about 25% by weight, for example, less than about 20% by weight, for example, less than about 15% by weight. Polyethylene particles may be present in the composition in an amount of more than about 5% by weight, for example, more than about 10% by weight, for example, more than about 15% by weight, for example, more than about 20% by weight, for example, more than about 25% by weight.

[0066]

[0067] During gel processing, the plasticizer is combined with high-density polyethylene particles, and such plasticizer can be substantially or completely removed during the formation of the polymer article. For example, in one embodiment, the resulting polymer article may contain polyethylene polymer in an amount greater than about 70% by weight, for example, greater than about 80% by weight, for example, greater than about 85% by weight, for example, greater than about 90% by weight, for example, greater than about 95% by weight.

[0067]

[0068] In general, any suitable plasticizer can be combined with various polyethylene polymers. The plasticizer may include, for example, hydrocarbon oils, alcohols, ethers, esters such as diesters, or mixtures thereof. Suitable plasticizers include, for example, mineral oil, paraffinic oils, and decalin. 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, and tetralin. In one embodiment, the plasticizer may include halogenated hydrocarbons, such as monochlorobenzene. Cycloalkanes and cycloalkenes can also be used, examples of which include camphene, methane, dipentene, methylcyclopentanediene, tricyclodecane, and 1,2,4,5-tetramethyl-1,4-cyclohexadiene. The plasticizer may also include mixtures and combinations of any of the above.

[0068]

[0069] Plasticizers are generally present in compositions used to form polymer articles in amounts of more than about 50% by weight, for example, more than about 55% by weight, for example, more than about 60% by weight, for example, more than about 65% by weight, for example, more than about 70% by weight, for example, more than about 75% by weight, for example, more than about 80% by weight, for example, more than about 85% by weight, for example, more than about 90% by weight, for example, more than about 95% by weight, for example, more than about 98% by weight. In fact, plasticizers may be present in amounts up to about 99.5% by weight.

[0069]

[0070] Polyethylene particles are blended with a plasticizer to form a uniform gel-like material.

[0071] To form a polymer article according to this disclosure, polyethylene particles are combined with a plasticizer and extruded through a die of a 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 into the extruder. According to this disclosure, to form a polymer article with few impurities, the plasticizer and particle mixture form a uniform gel-like material before exiting the extruder.

[0070]

[0072] In one embodiment, an elongated article is formed during a gel spinning or extrusion process. The polymer article may be in the form of, for example, fibers or films, such as membranes.

[0071]

[0073] During the process, at least a portion of the plasticizer is removed from the final product. The plasticizer removal process can occur by evaporation if a relatively volatile plasticizer is used. Otherwise, the plasticizer may be removed using an extractant. The extractant may contain, for example, a hydrocarbon solvent. An example of an extractant is dichloromethane. Other extractants include acetone, chloroform, alkanes, hexene, heptene, alcohols, or mixtures thereof.

[0072]

[0074] If necessary, the resulting polymer article can be stretched at a temperature raised below the melting point of the polymer mixture to increase its strength and modulus. Suitable temperatures for stretching are approximately in the range of ambient temperature to about 155°C. The stretching ratio is generally greater than about 4, for example, greater than about 5, for example, greater than about 6, for example, greater than about 7, for example, greater than about 8. The stretching ratio is generally less than about 15, for example, less than about 12, for example less than about 10, for example less than about 9, for example less than 8. According to this disclosure, the polymer article may be uniaxially stretched or biaxially stretched. The above stretching ratios can be used in either direction. The stretching ratio in one direction may be different from or the same as the stretching ratio in the other direction.

[0073]

[0075] In one aspect, porous membranes having a stretch factor generally greater than about 5, for example greater than about 6, and less than about 10, for example less than about 9, for example less than about 8, are fabricated according to this disclosure. It is thought that using a relatively high stretch factor can cause orientation of polymer chains. Orienting polymer chains in a predetermined direction can dramatically increase the strength in that direction of orientation. Stretching the membrane also reduces its thickness. Therefore, one aspect of this disclosure is directed towards stretching a film or membrane in one or both directions in order to reduce its thickness and also cause molecular orientation. In this way, a thin but strong porous membrane can be formed, especially when using at least one high molecular weight polyethylene polymer as described above.

[0074]

[0076] Polymer articles produced in accordance with this disclosure have a wide range of uses and applications. For example, in one embodiment, the process is used to produce membranes. Porous membranes can be used, for example, as battery separators. Alternatively, porous membranes can be used as microfilters. When fibers are produced, the fibers can be used to produce nonwoven fabrics, ropes, nets, and the like. In one embodiment, the fibers can be used as filler material in bulletproof clothing.

[0075]

[0077] Referring to Figure 1, one embodiment of a lithium-ion battery 10 fabricated according to the present disclosure is shown. The battery 10 comprises an anode 12 and a cathode 14. The anode 12 may be made from, for example, lithium metal. The cathode 14, on the other hand, may be made from sulfur or from an intercalated lithium metal oxide. According to the present disclosure, the battery 10 further comprises a porous membrane 16 or separator placed between the anode 12 and the cathode 14. The porous membrane 16 allows the passage of ions, such as lithium ions, while minimizing electrical short circuits between the two electrodes. As shown in Figure 1, in one embodiment, the porous membrane 16 is a single layer polymer membrane and does not include a multilayer structure. In one aspect, the single layer polymer membrane may also include a coating. The coating may be an inorganic coating made from, for example, aluminum oxide or titanium oxide. Alternatively, the single layer polymer membrane may also include a polymeric coating. The coating can increase heat resistance.

[0076]

[0078] Porous membranes fabricated according to this disclosure may generally have a thickness of about 2 micrometers to about 100 micrometers, including all ranges between them in 0.1 micrometer increments. When forming a porous membrane for an electrolytic cell, the membrane may have a thickness of about 2 micrometers to about 20 micrometers on one side, including all ranges between them in 0.1 micrometer increments. In one embodiment, it is possible to produce a porous membrane that is relatively thin but still has excellent strength properties. For example, the porous membrane may have a thickness of less than about 7.4 micrometers, e.g., less than about 6.8 micrometers, e.g., less than about 6.4 micrometers, e.g., less than about 5.9 micrometers, e.g., less than about 5.7 micrometers, e.g., less than about 5.5 micrometers, e.g., less than about 5.3 micrometers, e.g., less than about 5.2 micrometers, e.g., less than about 4.9 micrometers, e.g., less than about 4.8 micrometers, and may have a thickness greater than about 2.2 micrometers, e.g., greater than about 2.6 micrometers, e.g., greater than about 3 micrometers, e.g., greater than about 3.2 micrometers.

[0077]

[0079] Alternatively, thicker porous films can also be produced according to this disclosure. Such films may have a thickness greater than about 6 micrometers, for example, greater than about 6.5 micrometers, for example, greater than about 7 micrometers, for example, greater than about 7.5 micrometers, for example, greater than about 8 micrometers, for example, greater than about 8.5 micrometers, for example, greater than about 9 micrometers, and may have a thickness of less than about 17 micrometers, for example, less than about 16 micrometers, for example less than about 15 micrometers, for example less than about 14 micrometers, for example less than about 13 micrometers.

[0078]

[0080] Porous membranes fabricated in accordance with this disclosure may generally have a porosity of about 20% to about 50%, including the entire range in 0.5% increments between them, especially when producing membranes for electrolytic cells. On one side, it is possible to produce porous membranes having a porosity greater than about 22%, for example, greater than about 25%, for example, greater than about 27%, for example, greater than about 29%, for example, greater than about 31%, for example, greater than about 33%, for example, greater than about 35%. Porous membranes may have a porosity of less than about 45%, for example, less than about 42%, for example, less than about 40%, for example, less than about 38%, for example, less than about 36%, for example, less than about 35%, for example, less than about 34%, for example, less than about 33%, for example, less than about 32%.

[0079]

[0081] The Guarley permeability of porous membranes fabricated according to this disclosure may generally range from approximately 50 seconds / 100cc to approximately 1,000 seconds / 100cc, including the entire range between them in 1-second / 100cc increments. Guarley permeability measures resistance to flow; therefore, lower values ​​indicate greater permeability. The Guarley permeability of a porous membrane prepared in accordance with this disclosure may be, for example, less than about 600 seconds / 100cc, for example less than about 550 seconds / 100cc, for example less than about 500 seconds / 100cc, for example less than about 475 seconds / 100cc, for example less than about 450 seconds / 100cc, for example less than about 425 seconds / 100cc, for example less than about 400 seconds / 100cc, for example less than about 375 seconds / 100cc, for example less than about 350 seconds / 100cc, for example less than about 325 seconds / 100cc, for example less than about 300 seconds / 100cc, for example less than about 275 seconds / 100cc, for example less than about 250 seconds / 100cc, for example less than about 225 seconds / 100cc, for example less than about 200 seconds / 100cc. In one embodiment, especially when producing a thin film, the Guarley permeability may be less than approximately 180 seconds / 100cc, for example less than approximately 170 seconds / 100cc, for example less than approximately 160 seconds / 100cc, for example less than approximately 150 seconds / 100cc, for example less than approximately 140 seconds / 100cc, for example less than approximately 130 seconds / 100cc. The Guarley permeability may be greater than approximately 90 seconds / 100cc, for example greater than approximately 100 seconds / 100cc, for example greater than approximately 105 seconds / 100cc, for example greater than approximately 110 seconds / 100cc, for example greater than approximately 115 seconds / 100cc, for example greater than approximately 120 seconds / 100cc.

[0080]

[0090] One or more nucleating agents may be present in the polymer composition in amounts greater than about 100 ppm, for example, greater than about 300 ppm, for example, greater than about 500 ppm, for example, greater than about 600 ppm, and may generally be present in amounts less than about 20,000 ppm, for example, less than about 10,000 ppm, for example, less than about 4,000 ppm, for example, less than about 2,000 ppm, for example, less than about 1,500 ppm, for example, less than about 1,000 ppm.

[0081]

[0091] In one embodiment, a heat stabilizer may be present in the composition. Examples of heat stabilizers, but not limited to, include phosphates, amine antioxidants, phenolic antioxidants, or any combination thereof.

[0082]

[0092] In one embodiment, an antioxidant may be present in the composition. Examples of antioxidants include, but are not limited to, aromatic secondary amines, benzofuranones, sterically hindered phenols, or any combination thereof.

[0083]

[0093] In one embodiment, a light stabilizer may be present in the composition. Examples of light stabilizers, but not limited to, include 2-(2'-hydroxyphenyl)-benzotriazole, 2-hydroxy-4-alkoxybenzophenone, nickel-containing light stabilizers, 3,5-di-tert-butyl-4-hydroxybenzoate, sterically hindered amines (HALS), or any combination thereof.

[0084]

[0094] In one embodiment, a UV absorber may be present in the composition instead of, or in addition to, a light stabilizer. Examples of UV absorbers include, but are not limited to, benzotriazoles, benzoates, or any combination thereof.

[0085]

[0095] In one embodiment, a halogenated flame retardant may be present in the composition. Examples of halogenated flame retardants, but not limited to these, include tetrabromobisphenol A (TBBA), tetrabromophthalic anhydride, dodecachloropentacyclooctadecadiene (dechlorane), hexabromocyclododecane, chlorinated paraffin, or any combination thereof.

[0086]

[0096] In one embodiment, a non-halogenated flame retardant may be present in the composition. Examples of non-halogenated flame retardants, but not limited to these, include resorcinol diphosphate tetraphenyl ester (RDP), ammonium polyphosphate (APP), phosphinic acid derivatives, triaryl phosphate, trichloropropyl phosphate (TCPP), magnesium hydroxide, aluminum trihydroxyoxide, and antimony trioxide.

[0087]

[0097] In one embodiment, a lubricant may be present in the composition. Examples of lubricants, but not limited to, include silicone oil, wax, molybdenum disulfide, or any combination thereof.

[0088]

[0098] In one embodiment, a colorant may be present in the composition. Examples of colorants include, but are not limited to, inorganic and organic-based coloring pigments.

[0099] In one respect, acid scavengers may be present in the polymer composition. Acid scavengers may include, for example, alkali metal salts or alkaline earth metal salts. The 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]

[0100] These additives can be used individually or in any combination thereof. Generally, each additive may be present in an amount of at least about 0.05 wt.%, for example, at least about 0.1 wt.%, for example, at least about 0.25 wt.%, for example, at least about 0.5 wt.%, for example, at least about 1 wt.%, and generally in an amount of less than about 20 wt.%, for example, less than about 10 wt.%, for example, less than about 5 wt.%, for example, less than about 4 wt.%, for example, less than 2 wt.%. If present, the total wt.% of all components, including all additives used in the polymer composition, will be 100 wt.%.

[0090]

[0101] This disclosure can be better understood by referring to the following examples. The following examples are provided below for illustrative purposes and are not intended to limit the scope. The following experiments were performed to demonstrate some of the benefits and advantages of the present invention. [Examples]

[0091] Example 1

[0102] Various different polyethylene polymer compositions were formulated, formed into films, and tested for various physical properties. More specifically, three different polyethylene polymers were blended together to form films. The resin compositions were prepared into films using conventional methods such as gel extrusion, biaxial stretching, and solvent extraction.

[0092]

[0103] The following polyethylene polymers were used: First polyethylene polymer: molecular weight 600,000 g / mol; Second polyethylene polymer: Molecular weight 2,000,000 g / mol.

[0093]

[0104] The third polyethylene polymer varied depending on the sample number. The table below shows the molecular weight of the third polyethylene polymer, as well as the amounts of the first and third polyethylene polymers added to form the blend. The remainder of the blend was the second polyethylene polymer.

[0094] [Table 1]

[0095]

[0105] Each of the formulations in the table above was combined with a plasticizer, and the mixture was extruded into a gel to form a film. The plasticizer was almost completely removed from the final product. The following results were obtained (pin puncture strength measured according to ASTM F1306):

[0096] [Table 2]

[0097]

[0106] As shown above, samples 4 and 5 had the best balance of characteristics.

[0107] Samples 1, 3, 4, 5, and 10 above were also tested for processability. For specific purposes, the pressure and screw torque during gel extrusion of the formulations were measured. The samples were compared to a reference sample, which contained only a second polyethylene polymer with a molecular weight of 2,000,000 g / mol. The results are illustrated in Figures 2 and 3. As shown in Figures 2 and 3, compositions prepared according to this disclosure are generally easier to process. This allows for lower energy requirements for film production and fewer drawbacks.

[0098] Example 2

[0108] Example 1 was repeated. Samples 1 and 4 from Example 1 were reproduced. The following formulations were also produced: Sample No. 11: 10% by weight of polyethylene polymer with a molecular weight of 600,000 g / mol; 10% by weight of polyethylene polymer with a molecular weight of 4,500,000 g / mol; and 80% by weight of polyethylene polymer with a molecular weight of 2,000,000 g / mol; Sample No. 12: 10% by weight of polyethylene polymer with a molecular weight of 600,000 g / mol; 10% by weight of polyethylene polymer with a molecular weight of 3,600,000 g / mol; and 80% by weight of polyethylene polymer with a molecular weight of 2,000,000 g / mol.

[0099]

[0109] Four formulations were formed into porous membranes and tested for their properties. The following results were obtained (pin puncture strength measured according to ASTM F1306).

[0100] [Table 3]

[0101] Example 3

[0110] The process described in Example 1 was repeated to produce and test further polymer films. More specifically, samples 1 and 4 from Example 1 were reproduced and compared to a porous film (sample 13) made from a single polyethylene polymer with an overall molecular weight of 1.7 million g / mol.

[0102]

[0111] The following results were obtained (pin puncture strength measured according to ASTM F1306).

[0103] [Table 4]

[0104] Example 4

[0112] The process described in Example 1 was repeated to produce and test further polymer films. Samples 1 and 4 were reproduced in this example. More specifically, thinner films with a thickness of less than 6 micrometers were produced in this example.

[0105]

[0113] The following results were obtained (pin puncture strength measured according to GB / T36363-2018).

[0106] [Table 5]

[0107] Example 5

[0114] Further polymer films were produced by repeating the process described in Example 1. In this example, very thin films with a thickness of less than 6 micrometers were produced. To produce the films, the machine direction stretching ratio was 6.5, while the transverse direction stretching ratio was 8.5. Samples 1 and 4 were reproduced to create the films. The following results were obtained (pin puncture strength measured according to GB / T36363-2018).

[0108] [Table 6]

[0109]

[0115] As described above, a porous membrane that is extremely thin and possesses excellent strength characteristics was produced.

[0116] These and other modifications and variations of the present invention can be carried out by those skilled in the art without departing from the essence and scope of the invention as described in more detail in the appended claims. In addition, it should be understood that aspects of the various embodiments may be replaced whole or in part. Furthermore, those skilled in the art will understand that the foregoing description is merely an example and is not intended to limit the invention as described further in such appended claims.

Claims

1. A porous membrane comprising at least one high molecular weight polyethylene polymer, (a) Thickness of approximately 2 micrometers to approximately 6.8 micrometers; (b) Pin penetration strength greater than 400 gf in accordance with GB / T 36363-2018; (c) Porosity of approximately 20% to approximately 50%; and (d) Gurley air permeability of approximately 110 seconds / 100cc to approximately 280 seconds / 100cc The porous membrane having the above-mentioned properties.

2. A porous membrane according to claim 1, having a basic weight of approximately 2.6 gsm to approximately 3.9 gsm.

3. A porous membrane according to claim 1 or 2, having a thickness of approximately 3 micrometers to approximately 5.8 micrometers.

4. A porous membrane according to any one of claims 1 to 3, having a pin puncture strength greater than about 410 gf in accordance with GB / T 36363-2018.

5. A porous membrane according to any one of claims 1 to 4, having a tensile strength greater than about 200 MPa, for example, greater than about 250 MPa, for example, greater than about 275 MPa in at least one direction.

6. The porous membrane according to claim 1, which is formed from at least two types of high molecular weight polyethylene polymers.

7. The porous membrane according to claim 1, which is formed from at least three types of high molecular weight polyethylene polymers.

8. The porous membrane is made from a first polyethylene polymer, a second polyethylene polymer, and a third polyethylene polymer, wherein the first polyethylene polymer has a molecular weight of about 200,000 g / mol to about 1,100,000 g / mol, for example, about 300,000 g / mol to about 1,000,000 g / mol, and the first polyethylene polymer is present in the porous membrane in an amount of about 3% to about 25% by weight, and the second polyethylene polymer is present in an amount of about 1.1 million g / mol to about 31% by weight. The porous membrane according to any one of claims 1 to 7, wherein the second polyethylene polymer has a molecular weight of 0 million g / mol, for example, about 1.2 million g / mol to about 2.9 million g / mol, and is present in the porous membrane in an amount of about 25% to about 85% by weight, and the third polyethylene polymer has a molecular weight of about 3.1 million g / mol to about 5.2 million g / mol, for example, about 3.2 million g / mol to about 4.6 million g / mol, and is present in the porous membrane in an amount of about 10% to about 35% by weight.

9. The porous membrane according to any one of claims 1 to 8, wherein the porous membrane is made from a first polyethylene polymer, a second polyethylene polymer, and a third polyethylene polymer, the first polyethylene polymer having a molecular weight of about 500,000 g / mol to about 700,000 g / mol and present in the porous membrane in an amount of about 8% to about 12% by weight, the second polyethylene polymer having a molecular weight of about 1.8 million g / mol to about 2.2 million g / mol and present in the porous membrane in an amount of about 65% to about 85% by weight, and the third polyethylene polymer having a molecular weight of about 3.3 million g / mol to about 3.8 million g / mol and present in the porous membrane in an amount of about 12% to about 25% by weight.

10. A porous membrane comprising a polymer blend containing at least one high molecular weight polyethylene polymer, wherein the high molecular weight polyethylene polymer has a molecular weight of about 3.2 million g / mol to about 4.6 million g / mol, and the porous membrane is (a) Tensile strength greater than approximately 160 MPa in at least one direction; (b) Porosity of approximately 25% to 38%; (c) Gurley air permeability of approximately 110 seconds / 100cc to approximately 400 seconds / 100cc; and (d) Puncture strength per unit weight greater than approximately 250 gf / gms according to ASTM test F1306 The porous membrane having the above-mentioned properties.

11. The porous membrane according to claim 10, having a thickness of approximately 2 micrometers to approximately 20 micrometers, for example, approximately 3 micrometers to approximately 17 micrometers.

12. The porous membrane according to claim 10 or 11, having a tensile strength greater than about 170 MPa, for example, greater than about 180 MPa, for example, greater than about 185 MPa, in at least one direction.

13. A porous membrane according to claim 10, 11, or 12, having a porosity of approximately 28% to approximately 35%.

14. A porous membrane according to any one of claims 10 to 13, having a Guarley permeability of approximately 175 seconds / 100cc to approximately 375 seconds / 100cc.

15. The porous membrane according to any one of claims 10 to 14, wherein the high molecular weight polyethylene polymer having a molecular weight of approximately 3.3 million g / mol to approximately 3.8 million g / mol is present in the porous membrane in an amount of approximately 10% to approximately 35% by weight.

16. A porous membrane made from a polymer blend, wherein the polymer blend comprises a first polyethylene polymer, a second polyethylene polymer, and a third polyethylene polymer, the first polyethylene polymer having a molecular weight of about 300,000 g / mol to about 1,000,000 g / mol and present in the porous membrane in an amount of about 3% to about 25% by weight, the second polyethylene polymer having a molecular weight of about 1.2 million g / mol to about 2.9 million g / mol and present in the porous membrane in an amount of about 25% to about 85% by weight, and the third polyethylene polymer having a molecular weight of about 3.2 g / mol to about 4.6 million g / mol and present in the porous membrane in an amount of about 10% to about 35% by weight.

17. The porous membrane according to claim 16, wherein the porous membrane is made from a first polyethylene polymer, a second polyethylene polymer, and a third polyethylene polymer, the first polyethylene polymer having a molecular weight of about 500,000 g / mol to about 700,000 g / mol and present in the porous membrane in an amount of about 8% to about 12% by weight, the second polyethylene polymer having a molecular weight of about 1.8 million g / mol to about 2.2 million g / mol and present in the porous membrane in an amount of about 65% to about 85% by weight, and the third polyethylene polymer having a molecular weight of about 3.3 million g / mol to about 3.8 million g / mol and present in the porous membrane in an amount of about 12% to about 25% by weight.

18. (a) Thickness of approximately 2 micrometers to approximately 6.8 micrometers; (b) Pin puncture strength greater than 400 gf according to GB / T 36363-2018; (c) Porosity of approximately 22% to approximately 38%; and (d) Gurley air permeability of approximately 110 seconds / 100cc to approximately 280 seconds / 100cc A porous membrane according to claim 16 or 17, having the features described above.

19. (a) Tensile strength greater than approximately 160 MPa in at least one direction; (b) Porosity of approximately 25% to 38%; (c) Gurley air permeability of approximately 110 seconds / 100cc to approximately 400 seconds / 100cc; and (d) Puncture strength per unit weight greater than approximately 250 gf / gms according to ASTM test F1306 A porous membrane according to claim 16 or 17, having the features described above.

20. The porous membrane according to any one of claims 16 to 19, wherein the porous membrane is biaxially stretched, and the porous membrane is stretched in at least one direction at a stretching ratio greater than 5, for example, greater than 6, and less than 10, for example, less than 9.

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