Low-extractable polyethylene resin and injection-molded part made therefrom

Abstract

To provide a polyethylene resin enabling reduced particulate components and reduced metal elution in the resin when employed as an injection-molded part such as a filter, fitting, or valve in contact with high-purity chemicals or ultrapure water, and further enabling low elution levels to be retained after long-term storage; and also to provide an injection-molded part made therefrom.SOLUTION: There is provided a polyethylene resin that is an ethylene-α-olefin copolymer and has a density of 945-955 kg / m3, an MFR of 1.0-50 g / 10 min, an Mw / Mn of 3.0-6.0, a content of components having a molecular weight of 1000 or less of 0.30 wt.% or less, an aluminum content of 10 ppm or less relative to the polyethylene resin, a magnesium content of 10 ppm or less relative to the polyethylene resin, and a silicon content of 1 ppm or less relative to the polyethylene resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to low-elution polyethylene resins and injection-molded parts made therefrom. [Background technology]

[0002] Semiconductors are manufactured through various processes such as film formation, resist coating, exposure, development, and etching, with cleaning accounting for approximately 30% of the total process. High-purity chemicals or ultrapure water are used as essential chemicals in semiconductor manufacturing. Semiconductor cleaning chemicals include sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, hydrogen peroxide, isopropyl alcohol, phosphoric acid, and ammonia water.

[0003] In recent years, with the remarkable development of the electronics industry, fine particles such as organic impurities and metallic impurities contained in high-purity chemicals or ultrapure water have become a cause of reduced yields and defects in semiconductor devices, and so in recent years, there has been an increasingly strict demand for reducing such fine particles and metallic impurities.To satisfy this strict demand, there has also been an increasing demand for cleanliness in the wetted parts of injection-molded parts through which high-purity chemicals or ultrapure water pass.Examples of injection-molded parts include filters, valves, and fittings.

[0004] A commonly used method for reducing such fine particles is to filter high-purity chemicals or ultrapure water, but no mention is made of organic impurities or metal impurities contained in the materials constituting the filter (see, for example, Patent Documents 1 to 6). Another method uses a specific tetrafluoroethylene copolymer, but tetrafluoroethylene copolymers have the drawback of being expensive (see, for example, Patent Document 7). Furthermore, a polyethylene fiber has been proposed for use in liquid filtration filters used in semiconductor manufacturing processes. The fiber is a sheath-core composite fiber having a core component and a sheath component made of polyethylene resin, and the total content of the metal elements Na, K, Ca, Fe, Cu, Mg, Mn, Li, Al, Cr, Ni, and Zn contained within the fiber is 40 ppm or less. However, this document only describes a pretreatment method for the proposed filter material, and does not mention fine particles after pretreatment (see, for example, Patent Document 8). Furthermore, a polyethylene having a specific molecular weight component has been proposed for a different purpose, but the amount of metal elution is not mentioned (see, for example, Patent Document 9). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-136413 [Patent Document 2] International Publication No. 2022 / 004217 [Patent Document 3] International Publication No. 2020 / 184306 [Patent Document 4] Special Publication No. 2022-525882 [Patent Document 5] Japanese Patent Publication No. 2022-126355 [Patent Document 6] Patent No. 6787165 [Patent Document 7] Patent No. 7164829 [Patent Document 8] Patent No. 6818038 [Patent Document 9] Patent No. 5620130 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a polyethylene resin and an injection-molded part made therefrom which the amount of elution of particles such as organic impurities and metallic impurities into high-purity chemicals or ultrapure water with which it comes into contact is extremely low. [Means for solving the problem]

[0007] As a result of extensive research to solve the above problems, the inventors discovered that by using polyethylene having specific properties such as density, melt flow rate, molecular weight determined by gel permeation chromatography (GPC), and metal content, injection-molded parts with low levels of polyethylene-derived fine particles and metal impurities derived from polymerization catalyst components can be obtained, leading to the development of the present invention.

[0008] That is, the embodiments of the present invention are [1] to [9] shown below.

[0009] [1] A polyethylene resin that is an ethylene-α-olefin copolymer and satisfies the following requirements (1) to (7):

[0010] (1) Density: 945 to 955 kg / m 3 (2) Melt flow rate at 190°C and a load of 2.16 kg is 2.0 to 50 g / 10 min. (3) The ratio (Mw / Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) determined by gel permeation chromatography (GPC) is 3.0 to 6.0. (4) In the molecular weight distribution curve obtained using GPC, the content of components with a molecular weight of 1000 or less is 0.30% by weight or less (5) Aluminum content of polyethylene resin is 10 ppm or less (6) Magnesium content of ethylene resin is 10 ppm or less (7) Silicon content of polyethylene resin is 1 ppm or less [2] The polyethylene resin according to [1] above, which does not contain any additives.

[0011] [3] An injection-molded part made of the polyethylene resin described in [1] or [2] above.

[0012] [4] After immersing the molded product in ultrapure water and storing it at 23°C for 7 days, the amount of particles of 0.1 μm or more that can be dissolved from the molded product is measured. [3] The injection-molded part according to the above [3], wherein the number of fine particles is 2 / mL or less.

[0013] [5] The injection-molded part according to [3] above, wherein the amount of metal eluted from the injection-molded part after immersion in ultrapure water and storage at 23°C for 7 days is 10 PPT or less.

[0014] [6] The injection molded part according to [3] above, which comes into contact with high-purity chemicals or ultrapure water.

[0015] [7] A filter made of the injection molded part described in [6] above.

[0016] [8] A joint consisting of the injection molded part described in [6] above.

[0017] [9] A valve made of the injection molded part described in [6] above. [Effects of the Invention]

[0018] The low-elution polyethylene resin of one embodiment of the present invention can be used to produce injection-molded parts with low levels of elution of fine particles derived from the polyethylene resin and metals derived from polymerization catalyst components. Furthermore, the low-elution polyethylene resin is suitable for filters, fittings, valves, etc., and can provide injection-molded parts with low levels of elution of fine particles and metals in contact with high-purity chemicals or ultrapure water, even after long-term storage. DETAILED DESCRIPTION OF THE INVENTION

[0019] The low elution polyethylene resin according to one embodiment of the present invention is an ethylene-α-olefin copolymer and has the following properties (1) to (7).

[0020] (1) Density: 945 to 955 kg / m 3 (2) Melt flow rate at 190°C and a load of 2.16 kg is 2.0 to 50 g / 10 min. (3) The ratio (Mw / Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) determined by gel permeation chromatography (GPC) is 3.0 to 6.0. (4) In the molecular weight distribution curve obtained using GPC, the content of components with a molecular weight of 1000 or less is 0.30% by weight or less (5) Aluminum content of polyethylene resin is 10 ppm or less (6) Magnesium content of polyethylene resin is 10 ppm or less (7) Silicon content of polyethylene resin is 1 ppm or less The polyethylene resin can be produced using a highly active catalyst such as a Ziegler catalyst or a metallocene catalyst, and is preferably a polyethylene resin using a Ziegler catalyst as a polymerization catalyst, since this produces a polyethylene resin with a particularly low amount of metal elution. Examples of Ziegler catalysts include highly active Ziegler catalysts composed of transition metal compounds such as titanium and zirconium, magnesium compounds, and organoaluminum compounds, and the polyethylene resin can be produced by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms in a ratio that gives the desired density.

[0021] Examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 4-methyl-1-pentene, 3-methyl-1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, and 1-eicosene.

[0022] The polymerization method for producing the polyethylene resin is preferably a slurry polymerization method using a polymerization solvent having 6 to 10 carbon atoms, such as normal hexane or normal heptane, because this method can produce a polyethylene resin having a low concentration of metal impurities that dissolve in high-purity chemicals or ultrapure water, and can reduce the amount of low-molecular-weight components that cause the generation of fine particles.The polymerization method is preferably a single-stage polymerization method in which ethylene and a catalyst are initially added all at once, because this method produces a narrow molecular weight distribution and can reduce the amount of low-molecular-weight components.

[0023] The polyethylene resin is specified in terms of density, MFR, molecular weight distribution (Mw / Mn), components with a molecular weight of 1000 or less, and amount of contained metals, as shown below.

[0024] That is, the density of the polyethylene resin (JIS K6922-1) is 945 to 955 kg / m 3 and preferably 948 to 953 kg / m 3 945kg / m 3 If the density is less than 955 kg / m, the eluted polymer components will increase, causing the generation of fine particles. 3 If it exceeds this value, the stress cracking resistance decreases, and the durability of the injection molded article is unfavorably deteriorated.

[0025] The polyethylene resin has a melt flow rate (MFR, JIS K6922-1) of 2.0 to 50 g / 10 min at 190°C under a load of 2.16 kg, preferably 3.0 to 20 g / 10 min, and more preferably 5.0 to 20 g / 10 min. If the MFR is less than 2.0 g / 10 min, the fluidity during injection molding may be poor, resulting in molding defects such as short shots. If the MFR is more than 50 g / 10 min, stress cracking resistance and impact resistance may decrease.

[0026] The ratio of Mw to Mn (Mw / Mn) of the polyethylene resin determined by GPC is 3.0 to 6.0, preferably 3.5 to 4.9. If the Mw / Mn is less than 3.0, the molecular weight distribution is narrow, resulting in poor fluidity during injection molding and possibly resulting in molding defects such as short shots. If the Mw / Mn is more than 6.0, the molecular weight distribution broadens and the amount of low molecular weight components increases, causing the generation of fine particles.

[0027] In the molecular distribution curve obtained using GPC of this polyethylene resin, the components with a molecular weight of 1000 or less are 0. If the content of components with a molecular weight of 1000 or less exceeds 0.30% by weight, the content of low molecular weight components will increase, and the number of fine particles eluted from the molded article will increase.

[0028] The aluminum and magnesium contents of the polyethylene resin are 10 ppm or less relative to the polyethylene resin, and the silicon content is 1 ppm or less relative to the polyethylene resin. If the aluminum, magnesium, and silicon contents are below the above ppm, the amount of metal elution into high-purity chemicals is small, so the concentration of metal impurities in chemicals can be suppressed. The amount of metal content is expressed in weight ppm as the ratio of metal to the total resin. The amount of metal content is obtained by incinerating the resin and then fusing it with alkali.

[0029] Furthermore, the polyethylene resin is preferably free of all additives such as antioxidants, light stabilizers, and neutralizing agents. Here, the neutralizing agents are fatty acid metal salts, such as calcium stearate and zinc stearate, and hydrotalcites, all of which dissolve in chemicals and become metal contaminants, and are therefore preferably free of neutralizing agents.

[0030] The polyethylene resin can be made into injection-molded parts by injection molding, injection blow molding, etc. In particular, a molding method using an injection molding machine installed in a clean room is preferred for producing clean injection-molded parts.

[0031] When an injection-molded article obtained using the polyethylene resin is immersed in ultrapure water and left to stand for 7 days at 23°C, the number of particles of 0.1 μm or larger eluted from the molded article is preferably 2 particles / mL or less. If the number of particles of 0.1 μm or larger is 2 particles / mL or less, the resin can be adapted to the miniaturization of semiconductors.

[0032] When an injection-molded article obtained using the polyethylene resin is immersed in ultrapure water and left to stand at 23°C for 7 days, the amount of metal elution from the molded article is preferably 10 PPT or less. If the amount of metal elution is 10 PPT or less, defects in semiconductor devices can be suppressed.

[0033] Injection molded parts obtained using this polyethylene resin include filters, joints, valves, etc. that come into contact with high-purity chemicals or ultrapure water.

[0034] The filter is used to filter out small amounts of foreign matter contained in high-purity chemicals or ultrapure water, and is composed of a filter and a housing to house the filter in. The filter is preferably a cartridge filter that can be easily attached and detached, and examples of such cartridge filters include pleated filters and mesh filters.

[0035] Couplings are used to connect pipes, tubes, etc., and examples of these include those with diameters of 5 to 250 mm. Specific examples of couplings include L-shaped elbows, T-shaped tees, sockets for extending pipes, etc., and reducing diameter couplings for connecting pipes with different diameters. These may also be unions or male connectors with threads. Furthermore, couplings may be integrally molded or may be made by combining multiple injection-molded parts.

[0036] Valves control or open / close the flow rate of high-purity chemicals or ultrapure water, and examples of such valves include those capable of controlling the flow rate from 0 to 1,000 L / min. Specific examples of valves include diaphragm valves, ball valves, needle valves, butterfly valves, and check valves. These valves may be formed by combining injection-molded bodies, valves, handles, levers, and the like. [Example]

[0037] The present invention will be described below with reference to examples, but is not limited to these examples. The test methods used in the examples and comparative examples are as follows.

[0038] (1) Density Measurement was carried out by the density gradient tube method in accordance with JIS K6922-1.

[0039] (2) MFR Measurement was carried out in accordance with JIS K6922-1 at 190°C under a load of 2.16 kg.

[0040] (3) Mw / Mn Measurements were performed by GPC using a Tosoh HLC-8321GPC / HT (columns: Tosoh TSKgel® guard column HHR and TSKgel® GMHHR-H) and 1,2,4-trichlorobenzene as the eluent. The molecular weight calibration curve was calibrated using polystyrene samples with known molecular weights.

[0041] (4) Components with a molecular weight of 1,000 or less The percentage of the integrated amount of components with a molecular weight of 1000 or less was calculated from the molecular weight distribution curve obtained by GPC measurement.

[0042] (5) Catalyst residue amount The polyethylene resin was incinerated and then fused with alkali to form a solution, which was used as a measurement solution. The aluminum, magnesium, and silicon contents in the sample were measured by ICP-AES measurement.

[0043] (6) Injection molding Using an injection molding machine MD100X i2.7 (manufactured by Niigata Machine Techno Co., Ltd.) with a 35 mm diameter extrusion screw, polyethylene resin was injection molded at a cylinder temperature of 200°C, a mold temperature of 40°C, and an injection speed of 20 mm / s to produce a sheet-like injection-molded product (10.8 cm x 15.0 cm x 0.3 cm). The obtained sheet-like injection-molded product was cut into a 2.0 cm x 10.0 cm x 0.3 cm sample for measuring fine particles and metal elution amounts.

[0044] (7) Number of fine particles The injection-molded body was placed in a glass container that had been washed with ultrapure water in a clean room at 23°C, and the container was filled with ultrapure water. After storing the container with the lid on for 7 days, the number of particles of 0.1 μm or larger in the filled water was measured using a particle counter (manufactured by Rion Co., Ltd., controller: KE-40B1, particle sensor: KS-42A). The number of particles in the filled water is expressed in particles / mL.

[0045] (8) Amount of metal elution The injection-molded body was placed in a glass container that had been washed with ultrapure water in a clean room at 23°C, filled to the brim with ultrapure water, and stored for 7 days. The amount of metal eluted in the filled water was measured using an inductively coupled plasma mass spectrometer (PerkinElmer, ELAN DRCII). The amount of metal eluted in the filled water is shown as PPT.

[0046] (9) Flow length evaluation Using an injection molding machine MD100X i2.7 (manufactured by Niigata Machine Techno Co., Ltd.) with a 35 mm diameter extrusion screw and a semicircular spiral flow mold with a wall thickness of 2 mm and a width of 7 mm, injection molding was performed at a cylinder temperature of 200°C, a mold temperature of 40°C, an injection speed of 30 mm / s, and an injection pressure of 100 MPa, and the flow length was measured. The flow length was expressed in cm, and a value of 50 cm or more was considered good.

[0047] Example 1 <Preparation of solid catalyst component> A 3-L glass flask equipped with a stirrer was charged with 30.0 g (1.23 mol) of metallic magnesium powder and 168.0 g (0.494 mol) of titanium tetrabutoxide. 192 g (2.59 mol) of n-butanol containing 1.5 g of iodine was added at 90°C over 2 hours. The mixture was stirred at 140°C for 2 hours under a nitrogen blanket while removing the evolved hydrogen gas. After the temperature was increased to 110°C, 26 g (0.125 mol) of tetraethoxysilane and 19 g (0.125 mol) of tetramethoxysilane were added and the mixture was stirred at 140°C for another 2 hours. 2.1 L of hexane was then added to obtain a homogeneous solution.

[0048] This homogeneous solution was placed in a 10 L stainless steel autoclave equipped with a stirrer. The internal temperature of the autoclave was maintained at 45°C, and 800 mL of a hexane solution containing 1.0 mol of diethylaluminum chloride and 0.5 mol of i-butylaluminum dichloride was added over 1 hour. The mixture was then stirred at 60°C for an additional 1 hour to generate particles. After the temperature was returned to 45°C, 1.04 kg (3.35 mol) of a 50% hexane solution was added over 2 hours. After the entire mixture was added, the mixture was stirred at 60°C for 1 hour to obtain a solid catalyst component. The resulting solid catalyst component was used to remove any remaining unreacted materials and by-products using hexane, and then used as a hexane slurry in the production of polyethylene resin.

[0049] <Production of Polyethylene A> To the first stage of a continuous polymerization reactor having an internal volume of 370 L, dehydrated and purified hexane was fed at 110 L / hour, tributylaluminum as an organoaluminum compound at 110 mmol / hour, a solid catalyst component at 0.4 g / hour, ethylene at 25.0 kg / hour, 1-butene at 0.65 kg / hour, and hydrogen at a concentration relative to ethylene of 0.15 mol / mol, while the temperature was kept at 85°C and the total pressure was kept at 30 kg / cm. 2Ethylene polymerization was carried out continuously under conditions of an average residence time of 3.4 hours. The hexane slurry containing the polymer was passed through a flash tank to remove unreacted hydrogen, ethylene, and 1-butene, and then dried to obtain an ethylene copolymer powder. The obtained powder was pelletized without the addition of any additives to obtain polyethylene A. The results of physical property measurements are shown in Table 1.

[0050] Polyethylene A was used to produce injection-molded articles, and the above-mentioned particle measurement and metal elution evaluation were carried out using the resulting injection-molded articles. In addition, the flow length was measured by injection molding at a cylinder temperature of 200°C and an injection pressure of 100 MPa. The results are shown in Table 1.

[0051] Example 2 <Production of Polyethylene B> Ethylene and 1-butene were copolymerized in hexane in the same manner as in Example 1, except that hydrogen was supplied at a concentration ratio to ethylene of 0.20 mol / mol., thereby obtaining an ethylene copolymer powder. The obtained powder was pelletized without the addition of any additives, thereby obtaining polyethylene B. The results of measuring the physical properties are shown in Table 1.

[0052] Polyethylene B was used to produce injection-molded articles, and the above-mentioned particle measurement and metal elution evaluation were carried out using the resulting injection-molded articles. In addition, the flow length was measured by injection molding at a cylinder temperature of 200°C and an injection pressure of 100 MPa. The results are shown in Table 1.

[0053] Example 3 <Production of Polyethylene C> Ethylene and 1-butene were copolymerized in hexane in the same manner as in Example 1, except that hydrogen was supplied at a concentration ratio to ethylene of 0.10 mol / mol., thereby obtaining an ethylene copolymer powder. The obtained powder was pelletized without the addition of any additives, thereby obtaining polyethylene C. The results of measuring the physical properties are shown in Table 1.

[0054] Polyethylene C was used to produce injection-molded articles, and the above-mentioned particle measurement and metal elution evaluation were carried out using the resulting injection-molded articles. In addition, the flow length was measured by injection molding at a cylinder temperature of 200°C and an injection pressure of 100 MPa. The results are shown in Table 1.

[0055] Comparative Example 1 <Production of Polyethylene D> Ethylene and 1-butene were copolymerized in hexane in the same manner as in Example 1, except that hydrogen was supplied at a concentration ratio to ethylene of 0.45 mol / mol and 1-butene was supplied at a rate of 0.15 kg / hour. An ethylene copolymer powder was obtained by copolymerizing the resulting powder without the addition of any additives. Polyethylene D was obtained. The results of measuring the physical properties are shown in Table 1.

[0056] Polyethylene D was used to produce injection-molded articles, and the above-mentioned particle measurement and metal elution evaluation were carried out using the resulting injection-molded articles. In addition, the flow length was measured by injection molding at a cylinder temperature of 200°C and an injection pressure of 100 MPa. The results are shown in Table 1.

[0057] Comparative Example 2 <Production of Polyethylene E> Dehydrated and purified hexane was supplied to the first stage of a continuous polymerization reactor having an internal volume of 370 L at 110 L / hour, tributylaluminum as an organoaluminum compound at 110 mmol / hour, a solid catalyst component at 0.4 g / hour, ethylene at 25.4 kg / hour, and hydrogen at a concentration relative to ethylene of 0.45 mol / mol, while the temperature was kept at 85°C and the total pressure was kept at 30 kg / cm. 2 The first stage of ethylene polymerization (low molecular weight fraction) was carried out continuously under the conditions of an average residence time of 3.4 hours. The MFR of the low molecular weight fraction was 35 g / 10 min and the density was 968 kg / m 3 It was.

[0058] The hexane slurry containing the first-stage polymer was subjected to removal of unreacted hydrogen and ethylene in a flash tank, and then introduced into a second-stage polymerization reactor with an internal volume of 545 L. While additional hexane was fed to this polymerization reactor at 45 L / hr, ethylene was fed at 21.5 kg / hr, 1-butene at 1.9 kg / hr, and hydrogen at a concentration relative to ethylene of 0.016 mol / mol, respectively, at a temperature of 80°C and a total pressure of 20 kPa / cm. 2 Ethylene polymerization (high molecular weight component) was carried out under the conditions of an average residence time of 3.3 hours. The melt flow rate of the high molecular weight component was 2.2 g / 10 min at 190°C and a load of 21.6 kg, and the density was 930 kg / m 3 The discharge from the second-stage polymerization reactor was sent to a flash tank to remove unreacted hydrogen, ethylene, and 1-butene, and after washing with hexane at 50 L / hour, a drying process was carried out to obtain a powder mixture of ethylene copolymers. The proportion of low molecular weight components was 55% by weight, and the proportion of high molecular weight components was 45% by weight. The powder obtained by the two-stage polymerization using the above manufacturing process was pelletized without the addition of any additives to obtain polyethylene E. The results of measuring the physical properties are shown in Table 1.

[0059] Polyethylene E was used to produce injection-molded articles, and the above-mentioned particle measurement and metal elution evaluation were carried out using the resulting injection-molded articles. In addition, the flow length was measured by injection molding at a cylinder temperature of 200°C and an injection pressure of 100 MPa. The results are shown in Table 1.

[0060] Comparative Example 3 The following commercially available high-density polyethylene was used as polyethylene F. The results of measuring the physical properties are shown in Table 1.

[0061] Tosoh Corporation, (product name) Nipolon Hard (registered trademark) 8300A (with additives) Polyethylene F was used to produce injection-molded articles, and the above-mentioned particle measurement and metal elution evaluation were carried out using the resulting injection-molded articles. In addition, the flow length was measured by injection molding at a cylinder temperature of 200°C and an injection pressure of 100 MPa. The results are shown in Table 1.

[0062] Comparative Example 4 The following commercially available high-density polyethylene was used as polyethylene G. The results of measuring the physical properties are shown in Table 1.

[0063] Tosoh Corporation, (product name) Nipotek (registered trademark) 06S84A (additive-free) Polyethylene G was used to produce injection-molded articles, and the above-mentioned particle measurement and metal elution evaluation were carried out using the resulting injection-molded articles. In addition, the flow length was measured by injection molding at a cylinder temperature of 200°C and an injection pressure of 100 MPa. The results are shown in Table 1.

[0064] [Table 1]

Claims

1. A polyethylene resin which is an ethylene-α-olefin copolymer and has the following properties (1) to (5): (1) Density: 945 to 955 kg / m ３ (2) A melt flow rate of 2.0 to 50 g / 10 min at 190°C and a load of 2.16 kg. (3) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) determined by gel permeation chromatography (GPC) is 3.0 to 6.

0. (4) In the molecular weight distribution curve obtained using GPC, the content of components with a molecular weight of 1,000 or less is 0.30% by weight or less. (5) Aluminum content of polyethylene resin is 10 ppm or less (6) Magnesium content of polyethylene resin is 10 ppm or less (7) Silicon content of polyethylene resin is 1 ppm or less

2. 10. The polyethylene resin of claim 1, which is additive-free.

3. An injection-molded part made of the polyethylene resin according to claim 1 or 2.

4. 4. The injection-molded part according to claim 3, wherein the number of particles of 0.1 μm or more eluted from the injection-molded part after immersion in ultrapure water and storage at 23° C. for 7 days is 2 particles / mL or less.

5. 4. The injection-molded part according to claim 3, wherein the amount of metal eluted from the injection-molded part after immersion in ultrapure water and storage at 23°C for 7 days is 10 PPT or less.

6. 4. The injection molded part of claim 3, which is contacted with high purity chemicals or ultrapure water.

7. A filter comprising the injection molded part of claim 6.

8. A joint made from an injection-molded part according to claim 6.

9. A valve comprising the injection molded part according to claim 6.

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