Porous membranes and polymer compositions for producing them

Abstract

Polymer compositions for producing gel extruded articles are described. The polymer composition contains one or more high-density polyethylene polymers combined with one or more olefin copolymers. To form gel extruded articles, the polymer composition is combined with a plasticizer. In one embodiment, the polymer composition is used to form a porous membrane for use as a separator in electronic devices. The presence of olefin copolymers can increase the adhesion of the membrane produced from the composition when placed in contact with the anode and / or cathode. When producing porous membranes, olefin copolymers can also reduce the shutdown temperature and increase the wettability properties.

Description

[Technical Field]

[0001] Related applications

[0001] This application claims priority pursuant to U.S. Provisional Application No. 63 / 504,876, filed May 30, 2023, and U.S. Provisional Application No. 63 / 568,680, filed March 22, 2024, both of which are incorporated herein by reference. [Background technology]

[0002]

[0002] Polyethylene polymers have a wide variety of uses and applications. For example, high-density polyethylene is a useful engineering plastic with a unique combination of abrasion resistance, surface lubricity, chemical resistance, and impact strength. They are used in the production of high-strength fibers for use in ropes and bulletproof molded articles, and in 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.

[0003]

[0003] One alternative method for producing fibers and other elongated parts from polyethylene polymer is a gel processing method, in which the polymer is combined with a solvent. The resulting gel is extruded to form fibers or films, which may be stretched in one or two directions. After the articles are formed, all of the solvent can be removed from the product.

[0004]

[0004] 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 can allow ions to pass through due to the porous nature of the material. The ion permeability characteristic of microporous polyethylene membranes makes the material particularly well suited for regulating electrochemical reactions within batteries.

[0005]

[0005] Considering the above, one of the important features of lithium-ion battery membranes is the compatibility between the membrane and other components contained in the electrochemical cell, such as the anode, cathode, and electrolyte solution.

[0006]

[0006] Another important feature of polyethylene membranes is their ability to have a relatively low shutdown temperature, which is referred to 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.

[0007]

[0007] In addition to the shutdown temperature, polyethylene films also have a meltdown temperature, which is the temperature at which the film loses its mechanical stability and rupture occurs. Ideally, polymer films have a relatively low shutdown temperature, but at the same time have a relatively high meltdown temperature to provide safety and stability for electrical devices such as batteries. [Overview of the project]

Problems to be Solved by the Invention

[0008]

[0008] This disclosure is generally directed to further improvements of high-density polyethylene articles formed by extrusion of gels. In one aspect, this disclosure is directed to producing a porous membrane that can be used in an electrochemical cell and has improved affinity or improved adhesion properties when placed in contact with an anode or a cathode. The porous membrane produced according to this disclosure may also have improved wettability. The above improvements can be realized without adversely affecting other properties of the porous membrane. In fact, in one aspect, a porous membrane can be produced that exhibits a lower shutdown temperature.

Means for Solving the Problems

[0009] summary

[0009] Generally, this disclosure is directed to polyolefin compositions well-suited for gel processing applications. More particularly, this disclosure is directed to a polymer composition containing at least one high-density polyethylene polymer well-suited for producing a microporous ion-permeable membrane that can be used as a separator in a battery. The polymer composition may contain a single type of high-density polyethylene polymer or may contain a blend of high-density polyethylene polymers. According to this disclosure, the polymer composition is formulated to have at least one improved feature or property. For example, a porous membrane produced according to this disclosure can exhibit an increased adhesive bond to an adjacent structure such as an anode or a cathode in an electrochemical cell. In addition, the porous membrane can also exhibit improved wettability, particularly improved wettability to an electrolyte solution found in a lithium-ion battery. The improved wettability increases the mobility of the ions contained within the lithium-ion battery, thereby increasing the efficiency and lifespan of the battery. In yet another aspect, a porous membrane can be produced according to this disclosure that exhibits an improved shutdown temperature.

[0010]

[0010] In one embodiment, for example, the present disclosure is directed to a porous membrane made from at least one high-density polyethylene polymer blended with an olefin copolymer. The polyethylene polymer may have a number average molecular weight greater than about 300,000 g / mol. On the other hand, the olefin copolymer may contain an ethylene vinyl acetate copolymer. The ethylene vinyl acetate copolymer may have a controlled amount of vinyl acetate monomer units. For example, the ethylene vinyl acetate copolymer may have a vinyl acetate monomer content of less than about 30% by weight, for example less than about 29% 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. The ethylene vinyl acetate may have a vinyl acetate monomer content of about 5% to about 29% by weight, for example about 5% to about 15% by weight, for example about 5% to about 12% by weight.

[0011]

[0011] The ethylene vinyl acetate copolymer may be present in the porous membrane in an amount of about 0.1% to about 30% by weight, for example, in an amount of about 0.1% to about 20% by weight, or for example, in an amount of about 0.3% to about 12% by weight. In one embodiment, the ethylene vinyl acetate copolymer may have a melt flow index of about 0.1 g / 10 min to about 20 g / 10 min, for example, about 0.1 g / 10 min to about 5 g / 10 min, when determined according to ASTM test D1238-20 at a temperature of 190°C and a load of 2.16 kilograms.

[0012]

[0012] In one aspect, the olefin copolymer may be present in the porous film in an amount sufficient to reduce the shutdown temperature of the membrane or film. For example, the porous membrane may have a shutdown temperature of from about 120°C to less than about 140°C, such as from about 120°C to about 138°C, such as from about 120°C to about 135°C, such as from about 120°C to about 133°C. The olefin copolymer may be present in the porous membrane in an amount sufficient to reduce the shutdown temperature by at least about 1.8°C, such as at least about 2.2°C, such as at least about 2.5°C, such as at least about 3°C, such as at least about 3.5°C, compared to the same porous membrane without the olefin copolymer.

[0013]

[0013] The porous membranes of the present disclosure may have enhanced wicking properties when tested against electrolyte solutions such as propylene carbonate. For example, the olefin copolymer may be present in the porous membrane in an amount sufficient to increase the wicking distance of the membrane when measured according to an immersion test using propylene carbonate. The wicking distance can be increased by an amount greater than about 10%, such as greater than about 20%, such as greater than about 30%, such as greater than about 35%, compared to a porous membrane without the olefin copolymer.

[0014]

[0014] In another aspect, olefin copolymers may also have an effect on the wettability of the porous membrane. For example, olefin copolymers may optionally be present in the porous membrane in an amount sufficient to reduce the membrane's contact angle when measured against water. For example, the membrane's contact angle can be reduced by more than about 4%, for example more than about 5%, for example more than about 6%, and for example more than about 7%, compared to the contact angle of a similar membrane that does not contain olefin copolymers. For example, the contact angle of the porous membrane against water may be less than about 105°, for example less than about 102°, for example less than about 100°, and for example less than about 98°.

[0015]

[0015] The molecular weight of at least one high-density polyethylene polymer may be greater than about 500,000 g / mol, for example, greater than about 650,000 g / mol, for example, greater than about 800,000 g / mol, for example, greater than about 1,000,000 g / mol, for example, greater than about 2,000,000 g / mol, and generally less than about 12,000,000 g / mol, for example less than about 10,000,000 g / mol. When used herein, the molecular weight is determined according to the Margolies formula.

[0016]

[0016] A porous membrane prepared according to this disclosure may be a monolayer membrane that does not contain a polypropylene polymer. If necessary, the membrane may be optionally coated with an inorganic coating or a polymer coating. Generally, the porous membrane may have a thickness of about 4 micrometers to about 25 micrometers. The porous membrane may generally have a Guarley permeability greater than about 50 seconds / 100 mL, for example, greater than about 70 seconds / 100 mL. The porosity of the membrane may be about 20% to about 60%, for example, about 25% to about 50%.

[0017]

[0017] Porous membranes prepared in accordance with this disclosure are 1740, 1240, and 1020 cm -1 ±20cm-1 For example, ±5cm -1 It can be characterized by an IR spectrum having a peak at [location].

[0018]

[0018] The disclosure is also directed toward polymer compositions for producing gel extruded articles. The polymer compositions include plasticizers, high-density polyethylene particles, and olefin copolymers, such as ethylene vinyl acetate copolymer.

[0019]

[0019] In one embodiment, the high-density polyethylene particles used to produce the film are less than about 500 micrometers, for example less than about 150 micrometers, and may generally have a volume-based median particle diameter (d50) greater than about 50 micrometers. In one embodiment, the olefin copolymer may have a median particle diameter within about 20% of the median particle diameter of the high-density polyethylene particles, for example within about 10%. The olefin copolymer particles may have a median particle diameter of, for example, about 70 micrometers to about 1000 micrometers, for example about 70 micrometers to about 700 micrometers, for example about 70 micrometers to about 600 micrometers, for example about 70 micrometers to about 200 micrometers.

[0020]

[0020] The ethylene vinyl acetate copolymer may have a vinyl acetate monomer content of less than about 30% by weight, for example, about 5% to about 29% by weight. The ethylene vinyl acetate copolymer may have a melt flow index of about 0.1 g / 10 min to about 20 g / 10 min. The ethylene vinyl acetate copolymer may be present in the polymer composition in an amount of about 0.1 to about 20% by weight.

[0021]

[0021] Various different materials can be used as plasticizers. For example, plasticizers may include mineral oil, paraffinic oil, hydrocarbon oil, alcohol, etc. For example, plasticizers may include decalin, xylene, dioctyl phthalate, dibutyl phthalate, stearyl alcohol, oleyl alcohol, decyl alcohol, nonyl alcohol, diphenyl ether, n-decane, n-dodecane, or mixtures thereof. In one embodiment, plasticizers may include C5-C12 hydrocarbons, for example, C5-C12 saturated hydrocarbons. For example, plasticizers may include heptane, hexane, paraffin, etc.

[0022]

[0022] The disclosure is also directed to polymer articles formed from the polymer compositions described above. Polymer articles can be produced by gel extrusion or gel spinning processes. Examples of polymer articles produced according to the disclosure include fibers, films, and membranes.

[0023]

[0023] During the formation of the polymer article, most of the plasticizer is removed. For example, on one side, more than 95% by weight of the plasticizer, for example more than about 98% by weight, is removed during the formation of the polymer article. As a result, the polymer article made according to this disclosure generally contains high-density polyethylene polymer in an amount of about 60% to about 99% by weight, for example, in an amount of about 80% to about 98% by weight. The polymer article may also contain olefin copolymer in an amount of about 0.1% to about 30% by weight, for example, in an amount of about 1% to about 12% by weight.

[0024]

[0024] The disclosure is also directed to a process for producing polymer articles. The process includes a step of forming a gel-like composition from the polymer composition described above. The gel-like composition is then extruded through a die to form a polymer article. The polymer article may include, for example, a porous membrane.

[0025]

[0025] In one embodiment, an extraction solvent such as dichloromethane is combined with the polymer composition before or during the formation of the polymer article. The extraction solvent can be used to facilitate the removal of plasticizers.

[0026]

[0026] Other features and aspects of this disclosure will be discussed in more detail below.

[0027] This disclosure can be better understood by referring to the following drawings. [Brief explanation of the drawing]

[0027] [Figure 1] Figure 1 is a cross-sectional view of an electronic device, such as a battery, incorporating a porous membrane fabricated according to this disclosure. [Figure 2] Figure 2 is a plot or graph illustrating the shutdown and meltdown temperatures of a porous membrane using impedance testing. [Figure 3] Figure 3 is a graph of data from the examples described later. [Figure 4] Figure 4 presents IR spectral data from compositions prepared in accordance with this disclosure. [Figure 5] Figure 5 shows one embodiment of a process for exposing a film fabricated according to this disclosure to a plasma source. [Modes for carrying out the invention]

[0028]

[0028] The repeated use of reference symbols in this specification and drawings is intended to represent the same or similar features or elements of the present invention. definition

[0029] The melt flow rate of high-density polyethylene polymer or polymer composition is measured according to ISO Test 1133 at 190°C and a load of 21.6 kg.

[0029]

[0030] The density of the polymer is determined according to ISO test 1183, g / cm³. 3 It is measured in units of [unit].

[0031] The median particle size (d50) is measured using laser diffraction / light scattering, for example, a suitable light scattering device from Horiba, Ltd.

[0030]

[0032] The average molecular weight of a polymer is determined using Margolies' formula.

[0033] The tensile modulus, tensile stress at yield, tensile strain at yield, tensile stress at 50% break, tensile stress at break, and tensile nominal strain at break are all measured according to ISO test 527-2 / 1B.

[0031]

[0034] Immersion tests can be used to determine the wicking characteristics of a film prepared according to this disclosure, following the procedure below.

[0035] For the immersion test, a glass container with the following dimensions is used: upper area of ​​20 x 10 cm (covered with a metal plate) / lower area (base) of 19 x 8 cm / height: 10 cm. Two sheets of filter paper are taped to the inside of the glass container. Then, 300 ml of propylene carbonate is filled into the container (fluid level: 2 cm). The container is covered with a metal plate, and the propylene carbonate can fill the gas space in 20 minutes.

[0032]

[0036] The membrane is cut into pieces (length: 70 mm, width: 7 mm) with scissors. This is done using nitrile gloves to prevent touching the membrane with bare hands. The pieces are placed on an anodic metal plate (140 mm x 70 mm, frame width: 10 mm, tilt: 80°) with the help of a magnet. The MD direction of the membrane is upward (= immersion direction).

[0033]

[0037] Next, the metal frame with the fixed membrane is moved 40 times through a deionizer to remove the charge. Then, the frame is placed in a container filled with propylene carbonate at room temperature, and the membrane is immersed in the propylene carbonate for a desired amount of time. The container is closed with a metal plate while the immersion is taking place. Various soaking distances of the membrane are measured every 30 minutes by taking photographs and measuring the distance using a suitable computer program.

[0034]

[0038] By comparing the immersion distances of the tested membranes, we can draw conclusions about their affinity for the battery electrolyte.

[0039] 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.

[0035]

[0040] 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.

[0036] 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.

[0037] 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 the five readings). Record this value as the thickness of the sample.

[0038] 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 3.2.1 and 3.2.2 to obtain the bulk thickness and bulk weight. The density is calculated to three significant figures as follows:

[0039] aD film = Density (film) = (Weight of sample) / (THK × square) D film = density of the sample (mg / mm³) 3 ) Wt = weight of the sample (mg) THK = Thickness of the sample (mm) Square = area of ​​the sample, (mm²) 2 ) bD polymer = Density (polymer) 0.95 (g / cm³) 3 ) D polymer: High density of raw materials, no pores.

[0040] c. Porosity = (1 - D film / D polymer) × 100%

[0041] Puncture strength, when used herein, is measured according to ASTM test D3763 and measures the membrane's ability to withstand the occurrence of holes or defects by external particles. This test is performed using a test device such as Instron's CEAST9340 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-speed puncture mode at 1.67 mm / sec. Puncture strength can be normalized by dividing it by the membrane thickness, with units of mN / micrometer.

[0041]

[0042] The thermal shrinkage of the membrane is determined by placing a membrane sample (3 inches x 3 inches) in an oven at 105°C for 1 hour. The shrinkage is calculated by measuring the size in the MD and TD directions before and after the heat treatment.

[0042]

[0043] The shutdown temperature of a porous polymer membrane is the temperature at which the membrane's pores close, preventing ions from passing through. For example, when tested according to an impedance test, the shutdown temperature of a porous polymer membrane is the temperature at which the impedance first increases above 800 ohms. The shutdown temperature of a porous polymer membrane is also the temperature at which the polymer membrane begins to melt and the pores close.

[0043]

[0044] The meltdown temperature of a porous membrane is the temperature at which the membrane loses its mechanical stability and breaks. In a thermomechanical analysis (TMA) test, the dimensional change of the membrane is measured while the sample is subjected to a temperature regime and a static force of 0.01 N is applied. This test is performed over a temperature range from 40°C to 200°C at a heating rate of 5°C / min. Data evaluation is made using a plot of dimensional change against temperature, and the meltdown temperature is indicated when the dimensional change increases and exceeds 1000 micrometers. This test can be performed using TA Instruments' Thermomechanical Analysis (TMA) Model Q400, a film / fiber probe, and an MCA cooling system.

[0044]

[0045] Porous polymer membrane shutdown and meltdown temperatures are illustrated, for example, in Figure 2.

[0046] The shutdown or meltdown temperature of polymer articles, such as microporous membranes, may vary depending on the type of test and equipment used to measure the shutdown temperature. In fact, the shutdown temperature can vary widely depending on the procedure used to make the determination, the molecular weight of the base resin, and the equipment. Therefore, any shutdown temperature reported for different products may be even lower if different tests or techniques are used.

[0045]

[0047] In this disclosure, the shutdown temperature of a polymer article or polymer composition, such as a porous membrane, may be determined according to an "impedance test," a "thermomechanical analysis test," and a "differential scanning calorimetry test." However, the impedance test is the only test that directly measures the shutdown temperature. The following tests are defined as follows:

[0046] Impedance test

[0048] The impedance spectroscopy setup consists of a glass measuring cell containing two steel electrodes. Following the impedance spectroscopy method, the sample is immersed in an electrolyte (1 M LiPF6 in 1:1 ethylene carbonate / dimethyl carbonate) and assembled into the cell between the electrodes. The measuring cell is then connected to an impedance spectrometer that records the impedance spectrum every 50 seconds at frequencies from 100 Hz to 100 kHz. The measuring cell is then placed in an oven and heated to 110°C to 150°C for 2 hours while continuously recording the impedance spectrum. Data evaluation is performed using a plot of impedance against temperature, with the shutdown temperature indicated by the midpoint of the impedance spike. An example plot is demonstrated in Figure 1, where the arrow indicates the shutdown temperature. This test may also be performed using the HCP-803 potentiostat, available from Biologic Science Instruments.

[0047] Thermomechanical analysis (TMA test)

[0049] In the TMA method, dynamic strain is measured with a force multiplier of 0.5 while the sample is subjected to a temperature regime and a static force of 0.2 N. This test is performed over a temperature range from room temperature (25–30°C) to 160°C at a heating rate of 2°C / min. The frequency is set to 0.1 Hz. Data evaluation is performed using a plot of dynamic strain against temperature, with the softening point indicated by the inflection point of the dynamic strain. This test may also be performed using a Perkin Elmer DMA8000 dynamic mechanical analyzer.

[0048] Differential scanning calorimetry (DSC test)

[0050] Using differential scanning calorimetry (DSC), the melting point of a sample can be determined according to ISO test number 11357 under the following conditions: The sample is heated from 0°C to 180°C at a heating rate of 10°C / min and held isothermally at 180°C for 5 minutes. After isothermally holding, the sample is cooled to 0°C at a heating rate of 10°C / min. Finally, the sample is heated to 180°C at a heating rate of 20°C. The sample is inactivated with nitrogen throughout all steps of the DSC procedure. This test may be performed using a DSC Q2000 calorimeter available from TA Instruments.

[0049]

[0051] Contact angle measurements are performed using a Kruss DSA100 instrument. A film sample (10 × 40 mm) is mounted on a microscope slide using double-sided adhesive tape. Electrostatic charge is dissipated by moving the prepared sample several times through the electrostatic discharge chamber of the U electrode. The sample is placed on the measuring device, and a 3.5 μl droplet of the test fluid (water or ethylene glycol) is placed on the film. After the droplet is placed, the contact angle is determined via software for 7 seconds (one measurement per second). These seven data points are averaged to obtain the contact angle at the point of measurement. All samples are measured at six different spots or configurations on each side, and all results are averaged to obtain the reported value.

[0050] Detailed explanation

[0052] 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 broader aspects of the present disclosure.

[0051]

[0053] Generally, this disclosure is directed toward polymer compositions well suited for producing extruded articles such as fibers, films, and, for example, porous membranes. The polymer composition contains at least one high-density polyethylene polymer in combination with an olefin copolymer. The olefin copolymer may include, for example, an ethylene vinyl acetate copolymer having a controlled amount of vinyl acetate units. Controlling the amount of vinyl acetate in the ethylene vinyl acetate copolymer has been found to dramatically improve many properties of the polymer composition, particularly when extruded into various articles such as fibers, films, and, for example, porous membranes.

[0052]

[0054] For example, by adding an olefin copolymer to a high-density polyethylene polymer, a film with increased adhesive properties can be produced. For instance, when a porous film is incorporated into an electrochemical cell such as a lithium-ion battery, the porous film of this disclosure adheres better to adjacent anodes and adjacent cathodes. Improving the adhesion between the porous film and the cathode or anode not only facilitates the production process of the electrochemical cell but also improves the properties of the cell. Improving the adhesion between the anode and cathode can, for example, result in greater conductivity and ion flow through the film.

[0053]

[0055] Combining olefin copolymers with one or more high-density polyethylene polymers can also produce porous membranes with lower shutdown temperatures. The reduction in shutdown temperature is particularly advantageous because it does not compromise other physical properties. Especially when incorporated into electrochemical cells such as lithium-ion batteries, even a small reduction in shutdown temperature can provide dramatic improvements in, for example, the safety and other functions of the porous membrane.

[0054]

[0056] The addition of an olefin copolymer to one or more high-density polyethylene polymers can also produce polymer articles, such as porous membranes, that have improved wettability, especially when tested against electrolytes. The porous membranes can also exhibit, for example, dramatically enhanced wicking properties. When incorporated into a battery, for example, the improved wettability helps reduce the soaking time of the battery membrane, thereby resulting in high productivity. In addition, the increased wettability with the electrolyte solution can increase the mobility of ions such as lithium ions, thereby significantly increasing the battery life. Further, the membranes made in accordance with the present disclosure may have improved wicking properties when in contact with the electrolyte solution.

[0055]

[0057] As described above, the polymer compositions and articles made from the compositions of the present disclosure generally contain one or more high-density polyethylene polymers. In one aspect, the polymer composition contains a blend of high-density polyethylene polymers. One or more high-density polyethylene polymers can form the major polymer component and the matrix polymer of the polymer composition. The high-density polyethylene polymer can have a density of about 0.93 g / cm 3 or greater, such as about 0.94 g / cm 3 or greater, such as about 0.95 g / cm 3 or greater, and generally has a density of less than about 1 g / cm 3 such as less than about 0.96 g / cm 3 such as less.

[0056]

[0058] The high-density polyethylene polymer may be made from units derived from more than 90% ethylene, such as units derived from more than 95% ethylene, or may be made from units derived from 100% ethylene. The polyethylene may be a homopolymer or a copolymer, such as a terpolymer having other monomer units.

[0057]

[0059] High-density polyethylene may be high molecular weight polyethylene, very high molecular weight polyethylene, and / or ultrahigh molecular weight polyethylene. "High molecular weight polyethylene" is defined as having at least about 3 × 10⁻⁶ molecular weight. 5 This refers to polyethylene compositions 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 the purposes of this specification, the molecular weights referred to herein are determined according to Margolies' formula ("Margolies molecular weight").

[0058]

[0060] "Very high molecular weight polyethylene" is approximately 3 x 10 6 Less than g / mol and approximately 1 × 10⁻⁶ 6 This refers to polyethylene compositions having a weight-average molecular weight higher than g / mol. In some embodiments, the molecular weight of a very high molecular weight polyethylene composition is approximately 2 × 10⁻⁶. 6 From g / mol to approximately 3 × 10 6 It is in the range of less than g / mol.

[0059]

[0061] "Ultra-high molecular weight polyethylene" is at least approximately 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.

[0060]

[0062] In one aspect, high-density polyethylene is a homopolymer of ethylene. In another embodiment, high-density polyethylene may be a copolymer. For example, high-density polyethylene 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, and 1-hexadecene. Also available herein are 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. However, the amount of non-ethylene monomers in the copolymer, if present, may be less than about 10 mol.%, for example less than about 5 mol.%, for example less than about 2.5 mol.%, for example less than about 1 mol.%, in which case mol.% is based on the total molar amount of monomers in the polymer.

[0061]

[0063] In one embodiment, high-density polyethylene may have a unimodal molecular weight distribution. Alternatively, high-density polyethylene 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, high-density polyethylene may exhibit more than two molecular weight distribution peaks, such that polyethylene exhibits a multimodal (e.g., trimodal, tetramodal, etc.) distribution. Alternatively, high-density polyethylene 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.

[0062]

[0064] Any method known in the art can be used to synthesize polyethylene. Polyethylene powder is typically produced by catalytic polymerization of ethylene monomer, 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.

[0063]

[0065] The molecular weight of polyethylene can be adjusted by adding hydrogen. Furthermore, temperature and / or the type and concentration of the co-catalyst may also be used to fine-tune the molecular weight. In addition, to avoid contamination and product contamination, the reaction may be carried out in the presence of an antistatic agent.

[0064]

[0066] Suitable catalyst systems include, but are not limited to, Ziegler-Natta type catalysts. Typically, Ziegler-Natta type catalysts are derived from combinations of transition metal compounds from groups 4 to 8 of the periodic table and alkyl or hydride derivatives of metals 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 porous, micronized materials such as silica or magnesium chloride. Such supports may be added during catalyst synthesis or obtained as chemical reaction products of the catalyst synthesis itself.

[0065]

[0067] 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.

[0066]

[0068] 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.

[0067]

[0069] 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, accompanied by the release of alkyl chloride, until no further alkyl chloride is released, and then the solid is removed from the soluble reaction product by washing several times with hydrocarbon.

[0068]

[0070] In further embodiments, catalysts supported on silica, such as the commercially available catalyst system Sylopol 5917, can also be used.

[0071] 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 to 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 include calcium, magnesium, and zinc stearate.

[0069]

[0072] 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 and group 4 metal complexes.

[0070]

[0073] In one embodiment, polyethylene particles are made from a polyethylene polymer having a relatively low bulk density, as measured according to DIN 53466. For example, in one embodiment, the bulk density is generally about 0.6 g / cm³. 3 It is less than, for example, about 0.4 g / cm³. 3 Less than, for example, about 0.35 g / cm³ 3Less than, for example, about 0.33 g / cm³ 3 Less than, for example, about 0.3 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. In one embodiment, the polymer is about 0.2 g / cm³ 3 ~Approx. 0.27g / cm 3 It has bulk density.

[0071]

[0074] 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 about 500 micrometers, for example, less than about 400 micrometers, for example less than about 300 micrometers, or for example less than about 200 micrometers. For example, the median particle size (d50) of polyethylene particles may be less than about 150 micrometers, for example less than about 125 micrometers. The median particle size (d50) is generally greater than about 20 micrometers. The powder particle size can be measured using a laser diffraction method in accordance with ISO 13320.

[0072]

[0075] 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.

[0073]

[0076] The molecular weight of polyethylene polymers may vary depending on the specific application. Polyethylene polymers may have an average molecular weight determined, for example, according to Margolies' formula. The molecular weight can be determined by first 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. The average molecular weight is generally greater than approximately 300,000 g / mol, for example greater than approximately 500,000 g / mol, for example greater than approximately 650,000 g / mol, for example greater than approximately 1,000,000 g / mol, for example greater than approximately 2,000,000 g / mol, for example greater than approximately 2,500,000 g / mol, for example greater than approximately 3,000,000 g / mol, for example greater than approximately 4,000,000 g / mol. The average molecular weight is generally less than approximately 12,000,000 g / mol, for example less than approximately 10,000,000 g / mol. In one respect, the number-average molecular weight of high-density polyethylene polymers may be less than approximately 4,000,000 g / mol, for example less than approximately 3,000,000 g / mol.

[0074]

[0077] Polyethylene may have viscosity numbers ranging from at least 100 mL / g, for example from at least 500 mL / g, for example from at least 550 mL / g, to less than about 6,000 mL / g, for example less than about 5,000 mL / g, for example less than about 4,000 mL / g, for example less than about 3,000 mL / g, for example less than about 1,000 mL / g, when determined using the concentration in 0.0002 g / mL of decahydronaphthalene according to ISO 1628 Part 3.

[0075]

[0078] High-density polyethylene 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%. Crystallinity can be measured using differential scanning calorimetry (DSC).

[0076]

[0079] Generally, when the high-density polyethylene particles described above are combined with a plasticizer before forming an article, they are present in the polymer composition in amounts ranging from 0% to a maximum of about 50% by weight. For example, the high-density polyethylene particles may be present in the polymer composition in amounts 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. The polyethylene particles may be present in the composition in amounts greater 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.

[0077]

[0080] According to this disclosure, one or more high-density polyethylene polymers are combined with olefin copolymers to improve at least one property of a polymer composition and / or one property of a polymer article made from the polymer composition. In one aspect, the olefin copolymer may generally be an ethylene vinyl acetate copolymer derived from at least one ethylene monomer and at least one vinyl acetate monomer. Certain embodiments of the copolymer can be selectively controlled to help achieve desired properties. For example, the vinyl acetate content of the copolymer can be selectively controlled to be relatively low. For example, commercially available ethylene vinyl acetate copolymers may contain vinyl acetate in an amount of up to about 60% by weight. However, it has been found that ethylene vinyl acetate copolymers with a relatively low vinyl acetate monomer content have better compatibility with one or more high-density polyethylene polymers when extruded together. A lower amount of vinyl acetate monomer results in the production of polymer articles with better mechanical properties, for example, less phase separation.

[0078]

[0081] In one respect, for example, an ethylene vinyl acetate copolymer may contain vinyl acetate monomer in a content of less than about 30% by weight, e.g., less than about 29% by weight, e.g., less than about 25% by weight, e.g., less than about 20% by weight, e.g., less than about 15% by weight, e.g., less than about 14% by weight, e.g., less than 13% by weight, and generally more than about 3% by weight, e.g., more than about 5% by weight, e.g., more than about 6% by weight, e.g., more than about 7% by weight, e.g., more than about 8% by weight, e.g., more than about 9% by weight, e.g., more than about 10% by weight, e.g., more than about 11% by weight.

[0079]

[0082] The melt flow rate or melt flow index of ethylene vinyl acetate copolymer is also relatively low. For example, the melt flow index of ethylene vinyl acetate copolymer may be less than about 20 g / 10 min, e.g., less than about 10 g / 10 min, e.g., less than about 8 g / 10 min, e.g., less than about 5 g / 10 min, e.g., less than about 4 g / 10 min, e.g., less than about 3 g / 10 min, and generally may be greater than about 0.1 g / 10 min, e.g., greater than about 0.8 g / 10 min, e.g., greater than about 1.2 g / 10 min. The melt flow index for ethylene vinyl acetate copolymer components can be measured according to ASTM test D1238-20 at a temperature of 190°C and a load of 2.16 kg.

[0080]

[0083] The density of ethylene vinyl acetate copolymer, when determined according to ASTM D1505-18, is approximately 0.900 to approximately 1.00 grams / cubic centimeter (g / cm³). 3 ) may be within the range of, in some embodiments, approximately 0.910 to approximately 0.980 g / cm³. 3 In some embodiments, the amount is approximately 0.920 to 0.975 g / cm³. 3 The melting point of the ethylene vinyl acetate copolymer may be in the range of, for example, about 70°C to about 115°C, and in some embodiments it may be about 80°C to about 110°C, and in some embodiments it may be about 95°C to about 105°C.

[0081]

[0084] Various techniques can be commonly used to form ethylene vinyl acetate copolymers with desirable properties. In one embodiment, the polymer is produced by copolymerizing an ethylene monomer and a vinyl acetate monomer under high pressure. Vinyl acetate can be produced from the oxidation of butane, thereby yielding acetic anhydride and acetaldehyde, which can be reacted together to form ethylidene diacetate. Ethylidene diacetate can then be thermally decomposed in the presence of an acid catalyst to form vinyl acetate monomer. Examples of suitable acid catalysts include aromatic sulfonic acids (e.g., benzenesulfonic acid, toluenesulfonic acid, ethylbenzenesulfonic acid, xylenesulfonic acid, and naphthalenesulfonic acid), sulfuric acid, and alkanesulfonic acids, such as those described in U.S. Patent No. 2,425,389 by Oxley et al.; U.S. Patent No. 2,859,241 by Schnizer; and U.S. Patent No. 4,843,170 by Isshiki et al. Vinyl acetate monomer can also be produced by reacting acetic anhydride with hydrogen in the presence of a catalyst instead of acetaldehyde. This process directly converts vinyl acetate from acetic anhydride and hydrogen, eliminating the need to produce ethylidene diacetate. In yet another embodiment, vinyl acetate monomer can be produced by reacting acetaldehyde with ketene in the presence of a suitable solid catalyst such as a perfluorosulfonic acid resin or zeolite.

[0082]

[0085] In addition to controlling the monomer content, in one respect, the particle size of olefin copolymers, such as the particle size of ethylene vinyl acetate copolymer, can be controlled when blended with one or more high-density polyethylene polymers. For example, the median particle size of ethylene vinyl acetate copolymer may be within about 60% of the median particle size of the high-density polyethylene polymer particles, for example, within about 50%, within about 40%, within about 30%, within about 20%, or within about 10%.

[0083]

[0086] In another respect, the particle size of an olefin copolymer, such as the particle size of ethylene vinyl acetate copolymer, may be even larger than the particle size of one or more high-density polyethylene polymers. For example, in one respect, high-density polyethylene particles can be combined with ethylene vinyl acetate copolymer in the form of pellets.

[0084]

[0087] In one aspect, ethylene vinyl acetate copolymer particles may have a median particle diameter greater than about 0.5 mm, for example greater than about 1 mm, for example greater than about 2 mm, and less than about 5 mm, for example less than about 4.5 mm. In another aspect, ethylene vinyl acetate copolymer particles may be produced and / or ground to have a median particle diameter of less than about 1000 micrometers, for example less than about 700 micrometers, for example less than about 500 micrometers, for example less than about 300 micrometers, for example less than about 200 micrometers, for example less than about 150 micrometers. The median particle diameter of ethylene vinyl acetate copolymer particles may be greater than about 50 micrometers, for example greater than about 75 micrometers, for example greater than about 100 micrometers, for example greater than about 200 micrometers, for example greater than about 300 micrometers, for example greater than about 400 micrometers, for example greater than about 500 micrometers, for example greater than about 600 micrometers.

[0085]

[0088] The amount of olefin copolymer or ethylene vinyl acetate copolymer incorporated into a polymer article made in accordance with this disclosure may vary depending on the specific application and desired results. Generally, a polymer article made in accordance with this disclosure may contain one or more ethylene vinyl acetate copolymers in amounts from about 0.1% by weight to about 30% by weight, including the entire range between them in 0.1% by weight increments. For example, a polymer article may contain one or more ethylene vinyl acetate copolymers in amounts greater than about 0.3% by weight, for example, greater than about 0.8% by weight, for example, greater than about 1% by weight, for example, greater than about 1.5% by weight, for example, greater than about 2% by weight, for example, greater than about 2.5% by weight, for example, greater than about 3% by weight, for example, greater than about 3.5% by weight, for example, greater than about 4% by weight, for example, greater than about 4.5% by weight, for example, greater than about 5% by weight. One or more ethylene vinyl acetate copolymers may be present in the polymer article in an amount of less than about 25% 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, for example, less than about 12% by weight, for example, less than about 10% by weight, for example, less than about 8% by weight, for example, less than about 6% by weight. In various embodiments, one or more vinyl acetate copolymers may be present in the polymer article in an amount of about 1% to about 12% by weight, for example, about 1.5% to about 4.5% by weight.

[0086]

[0089] In addition to one or more olefin copolymers, the polymer compositions of the present disclosure may also contain a compatibilizer, which helps to compatibilize a blend of one or more ethylene vinyl acetate copolymers and one or more high-density polyethylene polymers. The compatibilizer may, for example, contain polyethylene polymers grafted onto the compatibilizer. The compatibilizer may contain, for example, maleic anhydride groups, acrylic acid groups, etc. The polyethylene grafted onto the compatibilizer may be high-density polyethylene polymers. The compatibilizer may be present in the grafted polymer in an amount greater than about 0.3% by weight, for example, greater than about 1% by weight, for example, greater than about 1.5% by weight, for example, greater than about 2% by weight, for example, greater than about 3% by weight, and generally in an amount less than about 25% by weight, for example, less than about 20% by weight, for example, less than about 15% by weight, for example, less than about 10% by weight. The compatibilizer may be present in the polymer article formed from the polymer composition in an amount greater than about 0.5% by weight, for example, greater than about 1% by weight, for example, greater than about 1.5% by weight, for example, greater than about 2% by weight, for example, greater than about 2.5% by weight, and generally in an amount less than about 25% by weight, for example, less than about 15% by weight, for example, less than about 10% by weight, for example, less than about 7% by weight, for example, less than about 5% by weight.

[0087]

[0090] To form a molded article according to this disclosure, a polymer composition containing one or more high-density polyethylene polymers, one or more olefin copolymers, and optionally one or more compatibilizers is combined with a plasticizer according to a process known as gel processing. During gel processing, one or more plasticizers are combined with the polymer composition, and the plasticizers can then be removed in the formation of the polymer article.

[0088]

[0091] For example, in one embodiment, the resulting polymer article may contain one or more high-density polyethylene polymers in an amount greater than about 50% by weight, for example, greater than about 60% by weight, for example, greater than about 70% by weight, for example, greater than about 80% by weight, for example, greater than about 90% by weight, for example, greater than about 95% by weight, for example, greater than about 97% by weight, and may generally contain less than about 98% by weight.

[0089]

[0092] In general, any suitable plasticizer can be combined with other components as long as the plasticizer forms a gel-like material suitable for gel spinning or extrusion. The plasticizer may include, for example, hydrocarbon oils, alcohols, ethers, esters such as diesters, or mixtures thereof. Suitable plasticizers include, for example, mineral oils, 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. Plasticizers may also include mixtures and combinations of any of the above.

[0090]

[0093] 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.

[0091]

[0094] To form a polymer article according to this disclosure, high-density polyethylene particles and olefin copolymer 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.

[0092]

[0095] 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.

[0093]

[0096] 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.

[0094]

[0097] 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 in the range of approximately ambient temperature to about 155°C. The stretching ratio is generally greater than about 4, for example, greater than about 6, greater than about 8, greater than about 10, greater than about 15, greater than about 20, greater than about 25, and greater than about 30. In certain embodiments, the stretching ratio is greater than about 50, greater than about 100, greater than about 110, greater than about 120, greater than about 130, greater than about 140, and greater than about 150. The stretching ratio is generally less than about 1,000, for example less than about 800, for example less than about 600, for example less than about 400. In one embodiment, a lower stretching ratio is used, for example, a stretching ratio of about 4 to about 10. The polymer article may be uniaxially stretched or biaxially stretched.

[0095]

[0098] In one embodiment, a porous membrane prepared according to this disclosure may optionally be subjected to plasma treatment, such as oxygen plasma treatment. Plasma treatment can further improve the compatibility of the porous polymer membrane with the electrolyte solution and increase its ionic conductivity.

[0096]

[0099] For example, in one aspect, the plasma process of the present disclosure is carried out using microwave discharge. In addition, the process can be carried out at very low pressure and extremely short contact time so as to preserve the physical properties of the porous polymer film.

[0097]

[0100] One embodiment of a plasma process that can be used in accordance with this disclosure is shown in Figure 5. Referring to Figure 5, the plasma process includes a microwave source 50 communicating with a vacuum chamber 52 via a cavity resonator 53. The cavity resonator 53 may include or be coupled to an impedance matching system. A substrate holder 54 is contained within the vacuum chamber 52. The vacuum chamber 52 is also coupled to a pressure monitoring device 58.

[0098]

[0101] To degas the chamber 52, the chamber 52 may be installed in communication with the pump 56. The vacuum chamber 52 may also be in communication with the exhaust port 60.

[0102] As shown in Figure 5, the vacuum chamber 52 may also be installed in fluid communication with one or more gas sources. In the embodiment illustrated in Figure 5, three different gas sources 62, 64, and 66 are shown. Each gas source 62, 64, and 66 is installed in connection with a corresponding mass flow controller 68, 70, and 72. The gas sources 62, 64, and 66 are for feeding oxygen to the vacuum chamber 52, either alone or in combination with other gases.

[0099]

[0103] As described above, in one embodiment, a microwave plasma reactor is used to deliver oxygen plasma to a porous polymer film. Other plasma reactors can be used according to this disclosure, but in one embodiment, a low-pressure plasma system with microwave discharge is preferred. Alternatively, an inductively coupled plasma system containing an RF generator can be used.

[0100]

[0104] During oxygen plasma treatment, the porous polymer film sample is placed in a vacuum chamber 52, which is degassed using a pump 56. The plasma produced by the microwave source 50 is then fed into the vacuum chamber 52 along with one or more oxygen-containing gases. The oxygen source may vary depending on the specific application. In one embodiment, pure oxygen gas is fed into the vacuum chamber 52. However, in an alternative embodiment, oxygen can be combined with other gases, such as inert gases. For example, oxygen can be combined with nitrogen. In one embodiment, air is fed into the plasma chamber 52. Other oxygen sources include hydrogen peroxide, water (water vapor), nitrous oxide, and ozone. In one embodiment, the gas fed into the plasma chamber 52 contains, on a volume basis, about 20% more oxygen, for example, about 30% more oxygen, or for example, about 50% more oxygen.

[0101]

[0105] During oxygen plasma treatment, an ionized gas is formed, which contains a variety of different cations and anions, and optionally includes free radicals, photons, and neutral chemical species. The ionized gas initiates reactions on the surface of the porous polymer film, which ultimately alters the chemical properties of the surface. For example, a polyethylene polymer may be oxidized in the presence of oxygen. The plasma-oxidized surface may contain a variety of different polar groups that increase the polarity of the porous polymer film surface, for example.

[0102]

[0106] The conditions inside the plasma chamber 52 during the plasma process are modifiable. In one embodiment, the oxygen plasma process is carried out at a low pressure. For example, the pressure inside the chamber may be maintained at less than 1 atmosphere. For example, the pressure inside the chamber may be less than about 10,000 Pa, for example less than about 5,000 Pa, for example less than about 1,000 Pa, for example less than about 500 Pa, for example less than about 300 Pa, for example less than 200 Pa. In one embodiment, the process is carried out at a very low pressure, for example less than about 150 Pa, for example less than about 130 Pa, for example less than about 100 Pa, for example less than about 80 Pa, for example less than about 50 Pa, for example less than 30 Pa. The temperature during the process may generally be below approximately 110°C, for example below approximately 100°C, for example below approximately 80°C, for example below approximately 60°C, for example below approximately 50°C, for example below approximately 40°C, for example below approximately 30°C, for example below approximately 28°C, for example below approximately 25°C, and may generally be higher than approximately 15°C, for example above approximately 20°C.

[0103]

[0107] According to this disclosure, the contact time between the porous polymer film and the oxygen plasma may be relatively short in one embodiment. For example, in one embodiment, each side of the porous polymer film may be exposed to the plasma for a period of less than about 30 seconds, for example, less than about 25 seconds, for example less than about 20 seconds, for example less than about 15 seconds, for example less than about 12 seconds, for example less than about 10 seconds, for example less than about 8 seconds, for example less than about 6 seconds. The contact time is generally longer than about 1 second, for example longer than about 2 seconds, for example longer than about 3 seconds. In particular, when the plasma generated by microwaves is used at low pressure, it has been found that very short contact times provide the required ionic conductivity without adversely affecting the physical properties of the film.

[0104]

[0108] 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 porous 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.

[0105]

[0109] 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 or co-extruded 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.

[0106]

[0110] Porous membranes fabricated in accordance with this disclosure may generally have a thickness greater than about 4 micrometers, for example, greater than about 5 micrometers, for example greater than about 6 micrometers, for example greater than about 7 micrometers, for example greater than about 8 micrometers, for example greater than about 9 micrometers, for example greater than about 10 micrometers, for example greater than about 11 micrometers. The membrane thickness is generally less than about 25 micrometers, for example less than about 20 micrometers, for example less than about 16 micrometers, for example less than about 14 micrometers, for example less than about 12 micrometers, for example less than about 10 micrometers.

[0107]

[0111] A membrane fabricated in accordance with this disclosure may have excellent physical properties. For example, a membrane having a porosity of about 20% to about 60%, for example, about 25% to about 50%, may have a puncture strength greater than about 800 mN / micrometer, for example, greater than about 980 mN / micrometer, for example, greater than about 1,060 mN / micrometer, for example, greater than about 1,100 mN / micrometer, for example, greater than about 1,200 mN / micrometer, and generally less than about 3,000 mN / micrometer.

[0108]

[0112] A film prepared in accordance with this disclosure may also have excellent tensile strength properties in either the longitudinal or widthwise direction. For example, in either direction, the film may have a tensile strength greater than about 115 MPa, e.g., greater than about 120 MPa, e.g., greater than about 125 MPa, and generally less than about 250 MPa.

[0109]

[0113] Polymer films prepared in accordance with this disclosure can withstand temperatures greater than approximately 50 seconds / 100ml, for example, greater than approximately 70 seconds / 100ml, for example, greater than approximately 80 seconds / 100ml, for example, greater than approximately 90 seconds / 100ml, for example, greater than approximately 105 seconds / 100ml, for example, greater than approximately 150 seconds / 100ml, for example, greater than approximately 200 seconds / 100ml, for example, greater than approximately 225 seconds / 100ml, for example, greater than approximately 250 seconds / 100ml, for example, greater than approximately 275 seconds / 100ml, for example, greater than approximately 300 seconds / 100ml, for example, greater than approximately 325 seconds / 100ml, for example, greater than approximately 350 seconds / 10 It may have a Guarley permeability greater than 0 ml, for example greater than approximately 375 seconds / 100 ml, for example greater than approximately 400 seconds / 100 ml, for example greater than approximately 425 seconds / 100 ml, for example greater than approximately 450 seconds / 100 ml, for example greater than approximately 475 seconds / 100 ml, for example greater than approximately 500 seconds / 100 ml, for example greater than approximately 525 seconds / 100 ml, for example greater than approximately 550 seconds / 100 ml, for example greater than approximately 575 seconds / 100 ml, for example greater than approximately 600 seconds / 100 ml, and generally it may have a Guarley permeability of less than approximately 1,000 seconds / 100 ml.

[0110]

[0114] Porous films fabricated according to this disclosure generally have a porosity greater than about 25%, for example, greater than about 30%, for example, greater than about 35%, and generally less than about 60%, for example, less than about 55%, for example, less than about 50%, for example, less than about 45%. In one aspect, the porosity may be about 35% to about 40%. In an alternative embodiment, the porosity may be about 39% to about 50%. The mean pore size may generally be greater than about 20 nm, for example, greater than about 23 nm, for example, greater than about 25 nm, for example, greater than about 26 nm, and generally less than about 70 nm, for example, less than about 60 nm, for example, less than about 50 nm, for example, less than about 45 nm, for example, less than about 40 nm, for example, less than about 35 nm.

[0111]

[0115] Polymer compositions can also dramatically enhance the ability of molded articles, such as porous membranes, to absorb fluids, particularly electrolyte fluids. For example, when subjected to immersion tests in propylene carbonate, the presence of olefin copolymers can increase the immersion distance and / or immersion rate after 10 hours by more than approximately 5%, for example, more than approximately 10%, for example, more than approximately 20%, for example, more than approximately 30%, for example, more than approximately 35%, compared to similar membranes that do not contain olefin copolymers. The immersion distance of a membrane can vary depending on many factors, such as the porosity and pore size of the membrane.

[0112]

[0116] In one respect, for example, the immersion distance of a membrane prepared according to this disclosure may be based on the air permeability of the porous membrane as well as the membrane thickness. For example, when tested in propylene carbonate, the immersion distance of a membrane prepared according to this disclosure is related to the following: Immersion distance (mm)≧-0.1473(x)+13.935 It may have the following, where x is the Gurley permeability (seconds / 100 mL) / thickness (micrometers). In other embodiments, the immersion distance may be greater than or equal to the following values: Immersion distance (mm)≧-0.1473(x)+15.00 Immersion distance (mm)≧-0.1473(x)+16.00.

[0113]

[0117] Porous membranes prepared in accordance with this disclosure can exhibit immersion rates in propylene carbonate of less than approximately 5 mm / hour, and are greater than approximately 0.55 mm / hour, for example, greater than approximately 0.6 mm / hour, for example, greater than approximately 0.7 mm / hour, for example, greater than approximately 0.75 mm / hour.

[0114]

[0118] Porous membranes fabricated in accordance with this disclosure may also exhibit a reduction in shutdown temperature. For example, olefin copolymers may be present in the membrane in an amount sufficient to reduce the shutdown temperature by more than about 0.5°C, for example more than about 0.8°C, for example more than about 1°C, for example more than about 1.2°C, for example more than about 1.6°C, for example more than about 1.8°C, for example more than about 2°C, for example more than about 2.4°C, for example more than about 2.8°C, for example more than about 3.2°C, for example more than about 3.6°C. The shutdown temperature of the membrane may be, for example less than about 140°C, for example less than about 138°C, for example less than about 136°C, for example less than about 135°C, for example less than about 134°C, for example less than about 133°C, for example less than about 132°C, for example less than about 131°C, for example less than about 130°C. The shutdown temperature is generally higher than about 120°C, for example higher than about 125°C.

[0115]

[0119] In addition to the properties and characteristics described above, polymer articles, particularly porous membranes, prepared in accordance with this disclosure also possess enhanced wettability when tested against water, depending on the surface roughness. For example, the olefin copolymers of this disclosure can be incorporated into polymer articles in an amount sufficient to optionally reduce the contact angle of the article by more than about 4%, for example, more than about 5%, for example, more than about 6%, for example, more than about 7%, when measured against water. Polymer articles, such as porous membranes, prepared in accordance with this disclosure may generally exhibit a contact angle greater than about 50°, for example, less than about 105°, for example less than about 102°, for example less than about 100°, for example less than about 98°, when measured against water.

[0116]

[0120] Among its specific advantages, one aspect is that olefin copolymers can be incorporated into polymer articles, particularly films such as porous membranes, that have improved adhesion properties to other structures. For example, by adding olefin copolymers to polymer articles, it is possible to produce porous membranes with greater adhesion properties when placed against anodes and cathodes. Greater adhesion between components can not only improve the structure of electrolytic cells but also lead to improvements in ionic conductivity and performance.

[0117]

[0121] Porous membranes fabricated in accordance with this disclosure are 1740, 1240, and 1020 cm². -1 ±20cm -1 For example, ±5cm -1 For example, ±1cm -1 It can be characterized by an IR spectrum having a peak at [location].

[0118]

[0122] Polymer compositions and polymer articles prepared in accordance with this disclosure may contain various other additives, such as heat stabilizers, light stabilizers, UV absorbers, acid scavengers, flame retardants, lubricants, colorants, and the like.

[0119]

[0123] In one embodiment, a heat stabilizer may be present in the composition. Examples of heat stabilizers include, but are not limited to, phosphates, amine antioxidants, phenolic antioxidants, or any combination thereof.

[0120]

[0124] 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.

[0121]

[0125] 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.

[0122]

[0126] 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.

[0123]

[0127] 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.

[0124]

[0128] 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.

[0125]

[0129] 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.

[0126]

[0130] 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.

[0131] 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, or salts of other organic acids, such as citrates. 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 tricalcium citrate, zinc oxide, calcium carbonate, magnesium oxide, and mixtures thereof.

[0127]

[0132] 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.%.

[0128]

[0133] 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]

[0129] Example 1

[0134] Various resin compositions containing a high-density polyethylene base resin were formulated. The high-density polyethylene polymer was combined with an ethylene vinyl acetate copolymer containing 12% by weight of vinyl acetate. The high-density polyethylene polymer had a molecular weight of 700,000 g / mol and an average particle size (d50) of approximately 115 micrometers. The polyethylene polymer had a melt flow rate of 0.5 g / 10 min. The two polymers were blended together using a tumble blender. The following samples were produced.

[0130] [Table 1]

[0131]

[0135] The resin composition was prepared into a film by conventional methods including gel extrusion, biaxial stretching, and solvent extraction.

[0136] The blend was gel-extruded using a resin and paraffin oil with a solid content of 30 wt.% at a temperature of approximately 190°C to 240°C at a screw speed of 200 rpm. After extrusion, the resulting film was solidified on a chill roller set to 40°C. Stretching was performed at a temperature of 120°C at a ratio of approximately 7x7 (MD / TD). Extraction of the stretched film was performed in acetone. The film was annealed at 120°C for 10 minutes.

[0132]

[0137] Next, the membrane was tested according to the immersion test using propylene carbonate, and the following results were obtained.

[0133] [Table 2]

[0134]

[0138] As shown above, samples prepared to contain ethylene vinyl acetate copolymer showed a dramatically increased immersion or wicking distance. Example 2

[0139] A porous membrane was produced by combining ethylene vinyl acetate copolymer with a high-density polyethylene polymer as described in Example 1. In this example, the ethylene vinyl acetate copolymer was contained in the polymer composition at an amount of 3.5% by weight. The remainder of the composition consisted of a high-density polyethylene polymer having a molecular weight of 700,000 g / mol.

[0135]

[0140] For comparative purposes, various porous membranes containing only high-density polyethylene polymer were formed.

[0141] Each porous membrane was subjected to an immersion test using propylene carbonate. As described above, it was found that the immersion distance depended on the Gurley permeability and membrane thickness of the porous membrane. Porous membranes made from a combination of high-density polyethylene polymer and ethylene vinyl acetate copolymer were labeled as sample number 4, while membranes made from high-density polyethylene polymer alone were labeled as sample number 5. For each produced membrane, the immersion distance was measured with respect to the Gurley permeability in seconds / 100 mL, divided by the membrane thickness in micrometers. The following results were obtained.

[0136] [Table 3]

[0137] [Table 4]

[0138]

[0142] The above results are illustrated with figures and tables in Figure 3. As shown, the porous membranes prepared according to this disclosure showed dramatically improved immersion distances compared to the reference sample. As shown, all samples prepared according to this disclosure had immersion distances in millimeters greater than the following relationship: Immersion distance (mm)≧-0.1473(x)+13.935 (In the formula, x is the Gurley permeability (seconds / 100 mL) / thickness (micrometers)).

[0139]

[0143] The membranes were also tested in terms of immersion rate, measured in millimeters per hour. Sample No. 5, prepared from reference data, showed an immersion rate of 0.5 mm / hour. However, the membrane of sample No. 4, prepared according to this disclosure, showed an immersion rate of 0.8 mm / hour. As a result, the membranes prepared according to this disclosure not only exhibit a greater immersion distance, but also exhibit such a distance at a rapid rate.

[0140]

[0144] The polymer composition used to produce the film of sample number 4 was also subjected to IR spectroscopy. The results are shown in Figure 4. As shown, the presence of ethylene vinyl acetate copolymer was observed at 1740 cm⁻¹. -1 , 1240cm -1 and 1020cm -1 This resulted in peak formation.

[0141]

[0145] 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 in whole or in part. Furthermore, it is expected that 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. An ion separator comprising a porous polymer film for separating an anode from a cathode, wherein the porous polymer film comprises a high-density polyethylene polymer blended with an olefin copolymer, the polyethylene polymer having a number average molecular weight greater than about 300,000 g / mol, the olefin copolymer comprises an ethylene vinyl acetate copolymer, the ethylene vinyl acetate copolymer having a vinyl acetate monomer content of less than about 30% by weight.

2. The ion separator according to claim 1, wherein the ethylene vinyl acetate copolymer has a vinyl acetate monomer content of about 5% to about 29% by weight, for example, about 5% to about 15% by weight, for example, about 8% to about 13% by weight.

3. The ion separator according to claim 1 or 2, wherein the ethylene vinyl acetate copolymer has a melt flow index of about 0.1 g / 10 min to about 20 g / 10 min, for example, about 0.1 g / 10 min to about 5 g / 10 min, when measured at a temperature of 190 °C and a load of 2.16 kg according to ASTM D1238-20.

4. The ion separator according to any one of claims 1 to 3, wherein the ethylene vinyl acetate copolymer is present in the porous polymer film in an amount of about 0.1% to about 30% by weight, for example, about 0.1% to about 20% by weight, for example, about 0.3% to about 8% by weight.

5. The ion separator according to any one of claims 1 to 4, wherein the polymer film has a shutdown temperature of about 120°C to less than 140°C, for example, about 120°C to about 138°C, for example, about 120°C to about 135°C, for example, about 120°C to about 133°C.

6. The ion separator according to any one of claims 1 to 5, wherein the olefin copolymer is present in the porous film in an amount sufficient to increase the immersion distance (mm) and / or immersion rate (mm / hour) in propylene carbonate by more than about 5%, for example more than about 10%, for example more than about 20%, for example more than about 30%, for example more than about 35%, after 10 hours, compared to a similar film that does not contain the olefin copolymer.

7. The ion separator according to any one of claims 1 to 6, wherein the porous polymer film has a thickness of about 4 micrometers to about 25 micrometers, for example, about 5 micrometers to about 15 micrometers, and has a porosity of about 20% to about 60%, for example, about 25% to about 50%.

8. The ion separator according to any one of claims 1 to 7, wherein the high-density polyethylene polymer is present in the porous film in an amount of about 60% to about 99% by weight, for example, about 80% to about 98% by weight.

9. The ion separator according to any one of claims 1 to 8, wherein the high-density polyethylene has a molecular weight greater than about 400,000 g / mol, for example greater than about 500,000 g / mol and less than about 12,000,000 g / mol.

10. The ion separator according to any one of claims 1 to 9, wherein the high-density polyethylene has a molecular weight greater than about 500,000 g / mol, for example, greater than about 850,000 g / mol and less than about 1,200,000 g / mol.

11. The ion separator according to any one of claims 1 to 10, wherein the ion separator is a single layer polymer porous film, and the film may optionally include a coating.

12. The ion separator according to claim 11, wherein the single layer polymer porous film includes a coating, and the coating includes an inorganic coating or a polymer coating.

13. The porous film has the following relationship: Immersion distance (mm) ≧ -0.1473 (x) + 13.935 An ion separator according to any one of claims 1 to 12, having an immersion distance in propylene carbonate according to the formula, where x is the Gurley permeability (seconds / 100 mL) / thickness (micrometers), and the porous film exhibits an immersion rate in propylene carbonate greater than about 5.5 mm / hour.

14. A polymer composition for producing gel extruded articles, Plasticizer; High-density polyethylene particles comprising at least one high-density polyethylene polymer, wherein the high-density polyethylene polymer has a number-average molecular weight greater than about 300,000 g / mol, and the high-density polyethylene particles have a volume-based median particle diameter of about 70 micrometers to about 500 micrometers; and Olefin copolymer particles, wherein the olefin copolymer comprises ethylene vinyl acetate copolymer, and the olefin copolymer particles have a volume-based median particle diameter of about 70 micrometers to about 5 mm. The polymer composition comprising the above.

15. The polymer composition according to claim 14, wherein the ethylene vinyl acetate copolymer has a vinyl acetate monomer content of about 5% to about 30% by weight, for example, about 5% to about 15% by weight, or for example, about 8% to about 14% by weight.

16. The polymer composition according to claim 14 or 15, wherein the ethylene vinyl acetate copolymer has a melt flow index of about 0.1 g / 10 min to about 20 g / 10 min, for example, about 0.1 g / 10 min to about 5 g / 10 min, when determined according to ASTM D1238-20 at a temperature of 190°C and a load of 2.16 kilograms.

17. The polymer composition according to any one of claims 14 to 16, wherein the ethylene vinyl acetate copolymer is present in an amount of about 0.1% to about 30% by weight, based on the total weight of the ethylene vinyl acetate copolymer and the high-density polyethylene polymer, for example, in an amount of about 0.1% to about 20% by weight, for example, about 0.3% to about 5% by weight.

18. The polymer composition according to any one of claims 14 to 17, wherein the high-density polyethylene polymer is present in the polymer composition in an amount of about 60% to about 99% by weight, for example, about 80% to about 98% by weight, based on the total weight of the ethylene vinyl acetate copolymer and the high-density polyethylene polymer.

19. The polymer composition according to any one of claims 14 to 18, wherein the high-density polyethylene has a molecular weight greater than about 400,000 g / mol, for example greater than about 500,000 g / mol and less than about 12,000,000 g / mol.

20. The polymer composition according to any one of claims 14 to 18, wherein the high-density polyethylene has a molecular weight greater than about 400,000 g / mol, for example greater than about 550,000 g / mol and less than about 1,200,000 g / mol.

21. The polymer composition according to any one of claims 14 to 20, wherein the high-density polyethylene particles have a volume-based median particle diameter of about 70 micrometers to about 210 micrometers, and the olefin copolymer particles have a volume-based median particle diameter of about 70 micrometers to about 5 mm.

22. The polymer composition according to any one of claims 14 to 21, wherein the plasticizer comprises mineral oil, paraffinic oil, hydrocarbon, alcohol, ether, ester, or a mixture thereof.

23. A polymer composition according to any one of claims 14 to 22, comprising only a single high-density polyethylene polymer or a blend of high-density polyethylene polymers.

24. The polymer composition according to any one of claims 14 to 21, 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, methylcyclopentanediene, tricyclodecane, 1,2,4,5-tetramethyl-1,4-cyclohexadiene, or a mixture thereof.

25. A polymer composition according to any one of claims 14 to 24, which does not contain polypropylene.

26. A process for producing polymer articles, A step of forming a gel-like composition from a polymer composition according to any one of claims 14 to 25; A process of extruding the gel-like composition through a die to form a polymer article. The process comprising the above, wherein the polymer article includes a film.

27. The process according to claim 26, further comprising the step of removing at least a portion of the plasticizer from the polymer article.

28. The process according to claim 27, wherein, during the process, an extraction solvent is added to the polymer composition to facilitate the removal of the plasticizer from the polymer article.

29. The process according to claim 28, wherein the extraction solvent comprises dichloromethane, acetone, chloroform, alkanes, hexene, heptene, alcohols, or mixtures thereof.

30. An ion separator comprising a porous polymer film for separating the anode from the cathode, wherein the porous polymer film comprises at least one high-density polyethylene polymer, and the porous polymer film has a density of 1740, 1240, and 1020 cm². －１ ±20cm －１ For example, ±5 cm －１ For example, ±1 cm －１ The ion separator described above, characterized by an IR spectrum having a peak at [a certain point].

31. An ion separator comprising a porous polymer film for separating an anode from a cathode, wherein the porous polymer film comprises at least one high-density polyethylene polymer blended with an ethylene vinyl acetate copolymer, the ethylene vinyl acetate copolymer present in the porous polymer film in an amount sufficient to increase the immersion distance (mm) and / or immersion rate (mm / hour) in propylene carbonate by more than about 5% after 10 hours compared to an equivalent film not containing the ethylene vinyl acetate copolymer.

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