High molecular weight polyethylene having narrow particle size distribution and excellent impregnability, and separator prepared therefrom

Abstract

Disclosed are a polyethylene which is a high molecular weight polyethylene for preparing a separator, and which has a narrow particle size distribution and excellent oil impregnation properties, and a separator prepared therefrom. The present invention provides a polyethylene prepared using a Ziegler-Natta catalyst having a viscosity average molecular weight (Mv) of from 500,000 g / mol to 3,000,000 g / mol, a particle size distribution (Span) of the powder of from 0.2 to 0.7, and a sphericity of the powder of more than 90% as determined by the following method.

Description

Technical Field

[0001] The present invention relates to a polyethylene and a separator prepared therefrom, and more particularly, to a high molecular weight polyethylene having a narrow particle size distribution and excellent impregnation properties and a separator prepared therefrom.

[0002] This application claims the priority and benefits of Korean Patent Application No. 10-2022-0165271, filed on November 30, 2022, and the entire text of the Korean patent application is incorporated herein by reference. Background Art

[0003] Secondary battery separator materials are prepared by a wet process using polyethylene. Such separators are mostly used as separators included in currently used secondary batteries, and their raw material is high molecular weight polyethylene.

[0004] In the preparation of separators, a method of impregnating polyethylene in oil for processing and then removing the oil to form micropores has been widely used commercially. The reason for using oil is not only to form micropores, but also because the molecular weight of polyethylene is continuously increasing currently, so in order to improve processability, impregnation is performed followed by extrusion.

[0005] Therefore, separator manufacturing companies are looking forward to polyethylene powder with a high molecular weight and excellent oil impregnation properties. Although they have recognized that to improve oil impregnation properties, polyethylene powder needs to have small and uniform particle sizes, there is no clear standard for its particle size level. Furthermore, it is also difficult to grasp other factors affecting impregnation properties other than particle size characteristics.

[0006] Korean Patent No. 2304973 discloses a polyethylene for separators, which is prepared by using a catalyst with a holding time of more than 4 hours for a reactivity of more than 50% of the initial reactivity, and has a relatively high molecular weight and a low average particle diameter, but does not mention content related to improving the particle size uniformity and impregnation properties of polyethylene powder. Summary of the Invention

[0007] The present invention aims to provide a polyethylene and a separator prepared therefrom, which is a high molecular weight polyethylene for preparing separators, having a narrow particle size distribution and excellent oil impregnation properties.

[0008] To solve the above problems, the present invention provides a polyethylene prepared by using a Ziegler-Natta catalyst, wherein the viscosity average molecular weight (Mv) of the polyethylene is 500,000 g / mol to 3,000,000 g / mol, the particle size distribution (Span) of the powder calculated according to the following Mathematical Formula 1 is 0.2 to 0.7, and the sphericity of the powder measured by the following method exceeds 90%.

[0009] [Mathematical Formula 1]

[0010] Span = (D 90 - D 10 ) / D 50

[0011] In the above mathematical formula 1, D 90 , D 50 and D 10 represent the particle sizes of the particles that are cumulatively 90%, 50%, and 10% respectively starting from the smallest particle in order of particle size;

[0012] [Method for Measuring Sphericity]

[0013] The sphericity of the powder particles was measured using an analytical device (Fluid Imaging Technologies, Flowcam 8100) for obtaining optical images and analytical software (visual spreadsheet).

[0014] In addition, a polyethylene is provided, characterized in that the ultraviolet transmittance of the polyethylene measured by the following method is less than 60%.

[0015] [Method for Measuring Ultraviolet Transmittance]

[0016] The polyethylene powder was mixed with paraffin oil at a content of 4% by weight, and the transmittance of the mixture was measured using a UV-visible spectrophotometer (UV-vis spectroscopy, uv-2550, Shimadzu), and the transmittance value was confirmed at 2.5 hours after mixing.

[0017] In addition, a polyethylene is provided, characterized in that the particle size distribution (Span) of the catalyst particles of the catalyst calculated according to the above mathematical formula 1 is 0.4 or less.

[0018] In addition, a polyethylene is provided, characterized in that the catalyst is a catalyst in which a titanium compound is supported on a magnesium carrier.

[0019] In order to solve the above another problem, the present invention provides a diaphragm made of the polyethylene.

[0020] The present invention provides a polyethylene which is a high molecular weight polyethylene for diaphragm prepared using a Ziegler-Natta catalyst, and the particle size distribution (Span) of its powder is 0.2 to 0.7, and the sphericity exceeds 90%, thereby providing a polyethylene with excellent oil impregnation property and a diaphragm prepared therefrom. Brief Description of the Drawings

[0021] Figures 1 to 3 They are scanning electron microscope (SEM) photos of polyethylene powders prepared according to the examples, Comparative Example 1, and Comparative Example 2 respectively. Detailed Description of the Invention

[0022] The preferred embodiments of the present invention will be described in detail below. When explaining the present invention, when it is judged that the detailed description of related well-known technologies may make the key points of the present invention unclear, the detailed description thereof will be omitted. Throughout the specification, when a certain part is mentioned as "including" a certain component, unless there is a particularly contrary record, it means that other components are not excluded, but other components can be further included.

[0023] The inventor of the present invention found that in order to improve the oil impregnation property of high molecular weight polyethylene for preparing diaphragms, not only does the powder need to have a narrow particle size distribution, but also the powder surface needs to have a certain roughness and be close to spherical. Based on this discovery, the present invention was completed.

[0024] Therefore, the present invention provides a polyethylene prepared using a Ziegler-Natta catalyst, wherein the viscosity average molecular weight (Mv) of the polyethylene is from 500,000 g / mol to 3,000,000 g / mol, the particle size distribution (Span) of the powder calculated according to the following Mathematical Formula 1 is from 0.2 to 0.7, and the sphericity of the powder measured according to the following method exceeds 90%.

[0025] [Mathematical Formula 1]

[0026] Span = (D 90 - D 10 ) / D 50

[0027] In the above Mathematical Formula 1, D 90 , D 50 and D 10 represent the particle sizes of the particles that are cumulatively 90%, 50% and 10% respectively from the smallest particle in the order of particle size;

[0028] [Method for Measuring Sphericity]

[0029] The sphericity of the powder particles is measured using an analysis device (Fluid Imaging Technologies, Flowcam8100) for obtaining optical images and analysis software (visual spreadsheet).

[0030] That is, when the polyethylene prepared using a Ziegler-Natta catalyst in the present invention has a viscosity average molecular weight (Mv), particle size distribution (Span), and sphericity within the above ranges, the polyethylene powder has a small average particle size and exhibits a uniform particle size, while having excellent oil impregnation properties. From this perspective, the particle size distribution (Span) of the powder is preferably from 0.2 to 0.6, and the sphericity of the powder is preferably more than 92%, more preferably more than 94%. In addition, if the melt index of the polyethylene is measurable, the melt index (at 190 °C, 21.6 kg load) is preferably from 0.1 g / 10 min to 1 g / 10 min, more preferably from 0.3 g / 10 min to 0.8 g / 10 min, and most preferably from 0.4 g / 10 min to 0.6 g / 10 min.

[0031] At this time, the average particle size of the polyethylene powder can be 200 μm or less, preferably 150 μm or less, more preferably 130 μm or less. In addition, the high molecular weight polyethylene is high density polyethylene, and its density can be 0.920 g / cm 3 to 0.950 g / cm 3 and is preferably from 0.930 g / cm 3 to 0.940 g / cm 3 .

[0032] Regarding the melt index and viscosity average molecular weight, if the melt index (only in the measurable case) is less than 0.1 g / 10 min and the viscosity average molecular weight exceeds 2,000,000 g / mol, problems such as process load will occur during the resin preparation process; if the melt index exceeds 1 g / 10 min and the viscosity average molecular weight is less than 1,000,000 g / mol, the mechanical properties will be insufficient when used as a separator.

[0033] On the other hand, the Ziegler-Natta catalyst used in the preparation of the polyethylene of the present invention can be a Ziegler-Natta type catalyst in which a titanium compound is supported on a magnesium carrier.

[0034] According to a specific example, the preparation of the Ziegler-Natta catalyst can be carried out through the following process: dissolving a magnesium compound in an alcohol-containing solvent to form a magnesium compound solution, adding a titanium compound and, if necessary, an internal electron donor to the magnesium compound solution to form a catalyst solution, precipitating the catalyst solution, washing the precipitate with a hydrocarbon solvent, and drying.

[0035] Examples of the titanium compound include: titanium tetrahalides such as TiCl4, TiBr4, TiI4; alkoxytitanium trihalides such as Ti(OCH3)Cl3, Ti(On-C4H9)Cl3, Ti(OC2H5)Br3; dialkoxytitanium dihalides such as Ti(OCH3)2Cl2, Ti(OC2H5)2Cl2, Ti(OC2H2)2Br2; monoalkoxytitanium trihalides such as Ti(OCH3)3Cl, Ti(OC2H5)3Cl, Ti(On-C4H9)3Cl, Ti(OC2H5)3Br; and tetraalkoxytitaniums such as Ti(OCH3)4, Ti(OC2H5)4, Ti(On-C4H9)4. Titanium tetrahalides are preferably used.

[0036] The hydrocarbon solvent used as a mixing agent for adjusting the concentration of the titanium compound should be an inert solvent that has no reactivity with the titanium compound. Examples of such hydrocarbon solvents include: aliphatic hydrocarbons such as pentane, hexane, heptane, octane, decane, dodecane, and kerosene; cycloaliphatic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and cyclooctane; and aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, isopropylbenzene, and cymene.

[0037] Examples of the magnesium compound include: magnesium halides such as magnesium chloride, magnesium bromide, magnesium iodide, and magnesium fluoride; alkoxymagnesiums such as ethoxymagnesium, isopropoxymagnesium, butoxymagnesium, and octoxymagnesium; alkoxychloromagnesiums such as methoxychloromagnesium and ethoxychloromagnesium; aryloxymagnesiums such as phenoxymagnesium and methylphenoxymagnesium; and aryloxychloromagnesiums such as phenoxychloromagnesium and methylphenoxychloromagnesium. These magnesium compounds can be used alone or in combination of two or more. Magnesium halides are preferably used.

[0038] When the magnesium compound reacts with an alcohol, although the reaction temperature varies depending on the type of hydrocarbon solvent used, it is generally 50°C or higher, preferably 70°C to 200°C. The reaction time can be 10 minutes to 5 hours, preferably 30 minutes to 3 hours.

[0039] The role of the alcohol is to dissolve the magnesium compound and form a bond with the magnesium compound in the catalyst, thereby forming appropriate pores to improve the catalyst performance. Any alcohol known in the art for use in the preparation of Ziegler-Natta catalysts can be appropriately used and is not particularly limited. For example, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, neopentanol, cyclopentanol, n-hexanol, cyclohexanol, methylcyclohexanol, n-heptanol, n-octanol, decanol, dodecanol, 2-methylpentanol, 2-ethylbutanol, 2-ethylhexanol, etc. can be used, and 2-methylpentanol, 2-ethylbutanol, 2-ethylhexanol, etc. are preferably used.

[0040] The reaction of the magnesium compound with the alcohol can be carried out in a suitable hydrocarbon solvent. At this time, the hydrocarbon solvent can be selected to only act as a simple dispersant and not participate in the reaction at all. As examples of available hydrocarbon solvents, alicyclic hydrocarbons such as pentane, hexane, heptane, octane, decane, dodecane, and kerosene can be cited.

[0041] The catalyst obtained by the above method can be in the form of solid particles, and its average particle size can be from 1 μm to 20 μm, preferably from 3 μm to 15 μm.

[0042] Here, if it is desired to prepare polyethylene powder with a narrow particle size distribution and improved sphericity, it is necessary for the particle size distribution of the prepared catalyst to be uniform. That is, regarding the catalyst in the present invention, the particle size distribution (Span) of the catalyst particles calculated according to the above mathematical formula 1 is preferably 0.4 or less, more preferably from 0.25 to 0.35.

[0043] If the particle size distribution of the catalyst exceeds 0.4, the polyethylene powder prepared will not only have a widened particle size distribution, but also the sphericity of the powder surface may be reduced. The preparation of a catalyst having such a particle size distribution is not particularly limited. For example, a catalyst having a target level of particle size distribution can be prepared by adjusting the feeding ratio of the magnesium compound solution and the titanium compound solution in the catalyst preparation process.

[0044] In the present invention, the preparation of polyethylene is not particularly limited, and the steps performed include a step of polymerizing ethylene in the presence of the catalyst. In a specific example, after mixing the catalyst with a cocatalyst, the reactor temperature is raised, and then hydrogen is introduced and ethylene is added for polymerization. At this time, the molecular weight of polyethylene can be adjusted by adjusting the amount of hydrogen introduced. For example, the amount of hydrogen introduced can be from 300 ppm to 800 ppm, and in order to obtain a molecular weight more suitable for the separator, it can be introduced in an amount of from 350 ppm to 700 ppm.

[0045] Generally, a substance having more than one M-C bond (M is a metal of Groups I to III in the periodic table) in the molecule can be used as the cocatalyst. As specific examples thereof, trialkylaluminums such as triethylaluminum and tributylaluminum; trienylaluminums such as triisopentenylaluminum; dialkylalkoxyaluminums such as diethylaluminum ethanolate and dibutylaluminum butanolate; dialkylalkoxyaluminums such as ethylaluminum ethanolate and dibutylaluminum butanolate; alkylaluminum sesquichlorides such as ethylaluminum sesquichloride and butylaluminum sesquichloride; dialkylaluminum hydrides such as dimethylaluminum hydride and dibutylaluminum hydride; alkylaluminum dihydrides such as ethylaluminum dihydride and propylaluminum dihydride; alkylaluminum alkoxyhalides such as ethylaluminum ethoxy chloride, ethylaluminum butoxy chloride, and ethylaluminum ethoxy bromide can be cited.

[0046] As described above, the prepared polyethylene is high molecular weight polyethylene, and the particle size distribution (Span) of its powder is 0.2 to 0.7, the sphericity exceeds 90%, and the oil impregnation property is excellent, which is very suitable for use in diaphragms.

[0047] Regarding the oil impregnation property of the polyethylene powder, after the polyethylene powder is impregnated in oil, when the ultraviolet transmittance is low according to the precipitation rate, it can be evaluated that the oil impregnation property is relatively excellent. The ultraviolet transmittance of the polyethylene prepared in the present invention measured by the following method can be lower than 60%, preferably lower than 55%.

[0048] [Method for measuring ultraviolet transmittance]

[0049] Mix the polyethylene powder with paraffin oil at a content of 4% by weight, and use an ultraviolet-visible spectrophotometer (UV-vis spectroscopy, uv-2550, Shimadzu) to measure the transmittance of the mixture, and confirm the transmittance value at the moment 2.5 hours after mixing.

[0050] Hereinafter, the present invention will be described by way of specific examples.

[0051] Example 1

[0052] (1) Preparation of catalyst

[0053] Under a nitrogen atmosphere, 3.0 g of magnesium chloride, 16 ml of 2-ethylhexanol, and 15 ml of decane were placed in a 0.5 L pressure-resistant glass reactor equipped with a stirrer and an oil circulation heater, and stirred at 80 °C at 300 rpm. In order to completely dissolve magnesium chloride, the temperature was raised to 135 °C, and the reaction was maintained for 1 hour after becoming a homogeneous solution. Then, the temperature was lowered to room temperature, 12.6 ml of hexane was added and the temperature was lowered again. When the temperature was maintained at 0 °C to -10 °C, it was stirred at 600 rpm and 16 ml of titanium tetrachloride (TiCl4) was slowly added. After the addition was completed, it was stirred while maintaining the temperature at 73 °C for 2 hours. Then, the temperature was lowered to 45 °C, the stirring was stopped, and the generated solid particles were allowed to precipitate. Then, after removing the supernatant, it was washed 5 times with 2 L of hexane and dried to obtain a catalyst.

[0054] (2) Preparation of polyethylene

[0055] In a 2L autoclave reactor purged with nitrogen (N2), 1,000 ml of hexane was filled as a solvent, and the moisture in the hexane was removed. Triethylaluminum (TEAL) (2 ml, 2 mmol) was added as a cocatalyst. Then, the prepared catalyst (1 g) was diluted in 100 ml of decane and the slurry-type catalyst (1 cc) was added. The valve of the reactor was closed, and the temperature of the reactor was raised to 80 °C. At this time, when the temperature of the reactor reached 70 °C, H2 was added, and ethylene was continuously added at 80 °C. The total reaction time was 2 hours, and the pressure of the reactor was maintained at 8.0 bar. After the reaction, the temperature of the reactor was lowered to room temperature. When the temperature inside the reactor dropped below 30 °C, the vent valve was slowly opened to reduce the pressure inside the reactor to atmospheric pressure. When the pressure inside the reactor became atmospheric pressure, the reactor was disassembled to obtain the polyethylene product. To remove hexane from the sample, filtration was performed using filter paper, and only the remaining polyethylene part after removing hexane was recovered and dried in a vacuum oven at 60 °C for 1 hour. By adjusting the hydrogen addition amount, the polyethylene powder described in Table 1 below can be obtained. To adjust the molecular weight, the hydrogen addition amount was adjusted to 450 ppm.

[0056] Comparative Example 1

[0057] Except for using the catalyst disclosed in Example 1 of Korean Patent No. 2304973 in the above example, polyethylene was prepared in the same manner as in Example 1 above.

[0058] Comparative Example 2

[0059] Except for adjusting the hydrogen addition amount to 830 ppm in Example 1 above, polyethylene was prepared in the same manner as in Example 1 above.

[0060] Comparative Example 3

[0061] Solid magnesium chloride was added to a hexane solution at 20 °C to form a slurry state, and then ethanol was added for swelling. Then, diethylaluminum chloride (DEAC) was added to remove the ethanol bonded to magnesium, and TiCl4 was added at this position for loading. Washing was performed in the same manner as the washing method of the catalyst in the above example. Using the obtained catalyst, polyethylene was prepared in the same manner as in Example 1 above.

[0062] Comparative Example 4

[0063] Except that the hydrogen dosage was adjusted to 830 ppm in Comparative Example 1 above, polyethylene was prepared in the same manner as in Comparative Example 1 above.

[0064] Example 2

[0065] Except that the hydrogen dosage was adjusted to 50 ppm in Example 1 above, polyethylene was prepared in the same manner as in Example 1 above.

[0066] Comparative Example 5

[0067] Except that the hydrogen dosage was adjusted to 50 ppm in Comparative Example 1 above, polyethylene was prepared in the same manner as in Comparative Example 1 above.

[0068] Example 3

[0069] Except that the hydrogen dosage was adjusted to 20 ppm in Example 1 above, polyethylene was prepared in the same manner as in Example 1 above.

[0070] Example 4

[0071] Except that the hydrogen dosage was adjusted to 5 ppm in Example 1 above, polyethylene was prepared in the same manner as in Example 1 above.

[0072] Test Example

[0073] The particle size distribution (SPAN), average particle size (APS), activity, melt index, viscosity average molecular weight, heat capacity, apparent density (BD), and sphericity of the catalysts and polyethylene powders of the above Examples and Comparative Examples were measured according to the following methods, and the results are shown in Table 1 below; the oil impregnation property was analyzed and evaluated according to the following methods, and the results are shown in Table 2 below. In addition, Figures 1 to 3 Scanning electron microscope (SEM) photographs of the polyethylene powders prepared according to Example 1, Comparative Example 1, and Comparative Example 3 are shown respectively.

[0074] [Analysis and evaluation methods]

[0075] (1) Particle size analysis of the catalyst

[0076] The APS (average particle size) was measured using a wet laser particle size analyzer of Malvern Instruments, and the Span value was calculated according to the following Mathematical Formula 1.

[0077] [Mathematical Formula 1]

[0078] Span = (D 90 - D 10 ) / D 50

[0079] In the above mathematical formula 1, D 90 , D 50 and D 10 represent the particle sizes at which the cumulative percentages are 90%, 50%, and 10% respectively, starting from the smallest particle in order of particle size.

[0080] (2) Particle size analysis of polyethylene powder

[0081] The APS (average particle size) and Span value of the polyethylene powder were measured using a sieve (allowing powders of 500 μm, 212 μm, 180 μm, 150 μm, 125 μm, 100 μm, 75 μm, and 45 μm to pass through).

[0082] (3) Catalyst activity

[0083] It was calculated using the ratio of the weight of the prepared polyethylene to the weight of the catalyst used in the polymerization of polyethylene.

[0084] (4) Apparent density (BD)

[0085] The polyethylene powder was measured according to ASTM D1895 standard.

[0086] (5) Melt index (MI)

[0087] The polyethylene powder was measured according to ASTM D1238 standard under the conditions of 190 °C and a load of 21.6 kg.

[0088] (6) Viscosity-average molecular weight (Mv)

[0089] After the sample was fully dissolved in decahydronaphthalene (Decalin) at a high temperature of 150 °C, the intrinsic viscosity (η) was measured using an AUTO IV Meter according to ISO 1628-3, and the molecular weight was calculated by the Margolies equation of the following mathematical formula 2.

[0090] [Mathematical formula 2]

[0091] Mv = 5.3×10 4 [η] 1.49

[0092] (7) Heat capacity

[0093] It was measured using a Differential scanning calorimetry (DSC), and the results of a three-step analysis at 200 °C and a heating rate of 10 °C / min were used.

[0094] (8) Sphericity

[0095] The sphericity of the powder particles was measured using an analytical device (FluidImaging Technologies, Flowcam 8100) for obtaining optical images and analytical software (visual spreadsheet).

[0096] (9) Oil impregnation property

[0097] The polyethylene powders prepared according to Example 1 and 2, Comparative Examples 1, 2, 4, and 5 above were mixed with paraffin oil at a content of 4% by weight, and the ultraviolet transmittance of the mixture was measured using an ultraviolet-visible spectrophotometer (UV-vis spectroscopy, uv-2550, Shimadzu). The ultraviolet transmittance values were confirmed immediately after mixing and at 2.5 hours in 30-minute intervals. If the ultraviolet transmittance value is low, this is a phenomenon caused by the sufficient penetration of the oil and the reduction of the precipitation rate, so it can be evaluated that the oil impregnation property is relatively excellent.

[0098] [Table 1]

[0099]

[0100] [Table 2]

[0101]

[0102] Referring to Table 1 and Table 2 and Figures 1 to 3 it can be seen that when polyethylene prepared using a Ziegler-Natta catalyst with a narrow particle size distribution according to the present invention and having a specific viscosity average molecular weight (Mv) or melt index, particle size distribution (Span), and sphericity (Example), the average particle diameter of the powder is 130 μm or less, the surface is rough, the ultraviolet transmittance is less than 55%, and the oil impregnation property is very excellent.

[0103] In contrast, when the particle size distribution (Span) of the polyethylene powder is wide and the sphericity is low because it is prepared using a catalyst with a wide particle size distribution (Span) (Comparative Examples 1, 4, and 6), it can be seen that the ultraviolet transmittance of the mixture after 2.5 hours in the ultraviolet transmittance experiment is 60% or more, and the oil impregnation property is poor.

[0104] In addition, even when prepared using a catalyst with a narrow particle size distribution (Span), when the molecular weight is too low or the melt index is too high (Comparative Example 2), it can be seen that the ultraviolet transmittance is 60% or more, and the oil impregnation property is poor.

[0105] In addition, the higher the molecular weight, the lower the density, and the slower the precipitation rate. In the oil impregnation experiment, although the molecular weight of Example 1 was lower than that of Comparative Examples 1, 3, and 5, the precipitation was slower, indicating that the polyethylene prepared according to the present invention has better kneadability with oil.

[0106] On the other hand, in the case of polyethylene in the ultra-high molecular weight region prepared by adjusting the hydrogen dosage during the polyethylene preparation process (Examples 2 to 4), it was also found that the particle size distribution (Span) of the polyethylene powder was narrow and the sphericity was high.

[0107] The preferred embodiments of the present invention have been described in detail above. The description of the present invention is only for illustration, and those with ordinary knowledge in the technical field to which the present invention pertains should understand that it can be easily deformed into other specific forms without changing the technical idea or essential features of the present invention.

[0108] Therefore, the scope of the present invention is defined by the claims, rather than by the above detailed description, and all modifications or variations based on the meaning, scope, and equivalent concepts of the claims should be construed as being included within the scope of the present invention.

Claims

1. A polyethylene prepared using a Ziegler-Natta catalyst, wherein the polyethylene has a viscosity-average molecular weight Mv of 500,000 g / mol to 3,000,000 g / mol, a span of the particle size distribution of the powder calculated according to the following Mathematical Formula 1 is 0.2 to 0.7, and the sphericity of the powder measured according to the following method exceeds 90%, [Mathematical Formula 1] Span=(D 90 -D 10 ) / D 50 In the above mathematical formula (1), D 90 , D 50 , and D 10 represent the particle sizes that are cumulatively 90%, 50%, and 10% respectively starting from the smallest particle in order of particle size; [Method for Measuring Sphericity] The sphericity of the powder particles is measured using an analytical device (Fluid Imaging Technologies, Flowcam 8100) for obtaining optical images and analytical software (visual spreadsheet).

2. The polyethylene according to claim 1, wherein the ultraviolet transmittance of the polyethylene measured according to the following method is less than 60%, [Method for Measuring Ultraviolet Transmittance] The polyethylene powder is mixed with paraffin oil at a content of 4% by weight, and the transmittance of the mixture is measured using an ultraviolet-visible spectrophotometer (UV-vis spectroscopy, uv-2550, Shimadzu), and the transmittance value is confirmed at 2.5 hours after mixing.

3. The polyethylene according to claim 1, wherein the span of the particle size distribution of the catalyst particles calculated according to the above Mathematical Formula 1 is 0.4 or less.

4. The polyethylene according to claim 1, wherein the catalyst is a catalyst in which a titanium compound is supported on a magnesium carrier.

5. A separator prepared from the polyethylene according to any one of claims 1 to 4.

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