Container

Abstract

Provided is a container in which there are few polyethylene-derived fine particles or polymerization catalyst component-derived metal impurities, and which has a low container inner surface roughness.　The container is formed from a polyethylene resin and satisfies characteristics (1)-(4). (1) When the container is filled with ultrapure water, the number of fine particles of at least 20 nm which dissolve from the container after stationary storage at 40°C for 35 days is at most 40 particles per mL; (2) when the container is filled with ultrapure water, the dissolved quantity of metal which dissolves from the container after being held stationary at 23°C for 7 days is at most 30 ppt; (3) the maximum roughness Rz of the container inner surface is at most 15.0 μm; and (4) the arithmetic average roughness Ra of the container inner surface is at most 1.5 μm

Description

container

[0001] This invention relates to a container made of polyethylene.

[0002] In recent years, with the remarkable development of the electronics industry, the demand for semiconductor cleaning chemicals has been increasing. Semiconductor cleaning chemicals are used as essential chemicals in the manufacture of electronic circuits such as large-scale, integrated LSIs. Specifically, sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, ammonium fluoride, hydrogen peroxide, isopropyl alcohol, xylene, TMAH (tetramethylammonium hydroxide), methanol, acetic acid, phosphoric acid, ammonia water, PGMEA (propylene glycol methyl ether acetate), DMSO (dimethyl sulfoxide), and NMP (N-methyl-2-pyrrolidone) are used for applications such as wafer cleaning and etching, wiring and insulating film etching, jig cleaning, developing solutions, resist diluents, resist stripping solutions, and drying.

[0003] The quality requirements for semiconductor cleaning chemicals have changed; previously, the metal impurity concentration was 1000 PPT or less, but now it is required to be less than 30 PPT. Furthermore, while the size of fine particles was previously problematic for particles between 100 and 200 nm, recently, particles as small as 30 nm have become a concern. Traditionally, polyethylene resin has been used as the container material for these semiconductor cleaning chemicals due to its chemical resistance, impact resistance, and cost. With the increasing integration density of semiconductor circuits, the demand for cleanliness in the containers that hold these chemicals is also increasing year by year in order to meet the quality requirements of semiconductor cleaning chemicals.

[0004] To solve this problem, a melt index of 0.1 to 8 g / 10 min and a density of 0.94 g / cm³ is used. ３ While the use of high-density polyethylene (HDPE) in hydrofluoric acid containers has been proposed, there is no mention of resin additives that may be contaminants (see Patent Document 1).

[0005] Furthermore, polyethylene containing a light-shielding agent forms the outer layer, and the innermost layer has a density of 0.958 g / cm³. ３As described above, containers for sulfuric acid and the like have been proposed with a number-average molecular weight of 5,000 to 12,000 and an Mw / Mn of 15 or more, and with specified concentrations of fatty acid metal salts and hindered phenol antioxidants, but the level of fine particles is low, at 0.5 μm or more (see Patent Document 2).

[0006] Furthermore, containers have been proposed that reduce the amount of hydrocarbon solvents extracted from polyethylene resin, suppress the content of low-molecular-weight components, and limit the amount of antioxidants, neutralizing agents, and lightfasteners added. However, improvements to address the effects of ash content due to residual catalytic components in the polyethylene resin are insufficient, and measures to address the concentration of metal impurities leaching into chemicals remain incomplete. In addition, the particle size is not sufficient at 0.2 μm or larger (see Patent Documents 3 and 4).

[0007] Furthermore, the density is 0.940–0.970 g / cm³ ３ High-purity polyethylene for chemical containers and high-purity chemical containers have been proposed, characterized by a melt flow rate of 2 to 50 g / 10 min at a temperature of 190°C and a load of 21.6 kg, a ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) of 8 to 15 determined by gel permission chromatography (GPC), and an ash content of 50 PPM or less in the polyethylene resin. However, improvements to address the influence of ash due to catalyst components remaining in the polyethylene resin are insufficient, and measures to address the concentration of metal impurities leaching into the chemicals remain incomplete (see Patent Document 5).

[0008] Japanese Patent Publication No. 5-41502 Publication No. 6-51399 Publication No. 7-62161 Publication No. 7-257540 Publication No. 11-80257

[0009] The present invention aims to provide a container that minimizes the leaching of contaminants such as polyethylene resin leaches and degraded materials into the contents of the container.

[0010] The inventors of the present invention, in order to manufacture a container made of polyethylene resin having specific properties, diligently investigated the manufacturing conditions during blow molding and found that it is possible to obtain a container with fewer polyethylene-derived fine particles and metal impurities derived from polymerization catalyst components, and a low inner surface roughness, leading to the development of the present invention.

[0011] In other words, the embodiments of the present invention are as follows: [1] to [5]. [1] A container made of polyethylene resin that satisfies the following characteristics (1) to (4): (1) The number of fine particles 20 nm or larger that leach from the container after filling it with ultrapure water and storing it at 40°C for 35 days is 40 particles / mL or less. (2) The amount of metal that leach from the container after filling it with ultrapure water and storing it at 23°C for 7 days is 30 PPT or less. (3) The maximum roughness Rz of the inner surface of the container is 15.0 μm or less. (4) The arithmetic mean roughness Ra of the inner surface of the container is 1.5 μm or less. [2] The container according to [1], wherein the polyethylene resin has the following properties (a) to (c): (a) Density is 0.940 to 0.965 g / cm³ ３ (b) Melt flow rate (MFR) at a temperature of 190°C and a load of 2.16 kg is 0.03 to 1.5 g / 10 min (c) Ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) determined by gel permeation chromatography (GPC) is 6.0 to 18 [3] The container according to [2] wherein the polyethylene resin has the following properties (d) to (g). (d) Melt flow rate (HLMFR) at a temperature of 190°C and a load of 21.6 kg is 3.0 to 60 g / 10 min (e) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 500 or less is 0.15% by weight or less (f) Metal content is 10 PPM or less relative to the polyethylene resin (g) Environmental stress crack resistance (ESCR) is 50 hours or more [4] A method for forming a container by blow molding a polyethylene resin having the following properties (a) to (c), wherein the temperature of the extruded molten resin (parison) is 170°C to 200°C, and the shear rate of the parison at the die exit is 30 to 100 s －１ A method for forming a container according to [1], characterized in that (a) the density is 0.940 to 0.965 g / cm³. ３(b) Melt flow rate (MFR) at a temperature of 190°C and a load of 2.16 kg is 0.03 to 1.5 g / 10 min (c) Ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) determined by gel permeation chromatography (GPC) is 6.0 to 18 [5] The method for molding a container according to [4] wherein the polyethylene resin has the following properties (d) to (g): (d) Melt flow rate (HLMFR) at a temperature of 190°C and a load of 21.6 kg is 3.0 to 60 g / 10 min (e) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 500 or less is 0.15% by weight or less (f) Metal content is 10 PPM or less relative to the polyethylene resin (g) Environmental stress crack resistance (ESCR) is 50 hours or more

[0012] According to the present invention, it is possible to provide a container for semiconductor cleaning chemicals that contains fewer fine particles derived from polyethylene resin and fewer metal impurities derived from polymerization catalyst components.

[0013] A container according to one aspect of the present invention is made of polyethylene resin and satisfies the following characteristics (1) to (4): (1) The number of fine particles 20 nm or larger that leach from the container after filling it with ultrapure water and storing it at 40°C for 35 days is 40 particles / mL or less. (2) The amount of metal leached from the container after filling it with ultrapure water and storing it at 23°C for 7 days is 30 PPT or less. (3) The maximum roughness Rz of the inner surface of the container is 15.0 μm or less. (4) The arithmetic mean roughness Ra of the inner surface of the container is 1.5 μm or less.

[0014] When ultrapure water is filled into the unwashed container, the number of particles larger than 20 nm that leach from the container is 40 particles / mL or less, preferably 35 particles or less, after storage at 40°C for 35 days. If the number of particles larger than 20 nm exceeds 40, it can cause disconnections in electronic circuits and deterioration of electrical characteristics, making it difficult to keep up with the miniaturization of LSIs.

[0015] When an unwashed container is filled with ultrapure water and left to stand at 23°C for 7 days, the amount of metal leached from the container is 30 PPT or less, preferably 10 PPT or less, and more preferably 7 PPT or less. If the amount of metal leached exceeds 30 PPT, it can cause disconnections in electronic circuits and deterioration of electrical properties, making it difficult to suppress defects in semiconductor devices. Examples of metals that leach from the container include Mg, Al, Ti, Cr, Zr, and Hf.

[0016] The maximum roughness Rz of the inner surface of the container is 15.0 μm or less, preferably 10.0 μm or less. If Rz exceeds 15.0 μm, the appearance of the molded product will be inferior. Furthermore, air bubbles in the chemicals will not remain in the rough areas and will not be detected as fine particles, thus preventing an increase in the number of fine particles. Rz is expressed by finding the sum of the height of the highest peak and the depth of the deepest valley in the roughness curve over a standard length.

[0017] Furthermore, the arithmetic mean roughness Ra of the inner surface of the container is 1.5 μm or less, preferably 1.0 μm or less. Ra represents the average value of the unevenness over a reference length.

[0018] The polyethylene resin used for this container has a low number of particulate matter particles and excellent chemical resistance, and its density (JIS K6922-1) is 0.940 to 0.965 g / cm³. ３ Preferably, it is 0.947 to 0.958 g / cm³. ３ It is preferable that this be the case.

[0019] Since the polyethylene resin exhibits excellent moldability and surface smoothness when used as a container, the MFR (JIS K6922-1) is preferably 0.03 to 1.5 g / 10 min, and more preferably 0.03 to 1.2 g / 10 min.

[0020] Since the polyethylene resin exhibits excellent chemical resistance and surface smoothness when used as a container, the ratio of Mw to Mn (Mw / Mn) determined by GPC is preferably 6.0 to 18, and more preferably 6.0 to 15.

[0021] The polyethylene resin exhibits particularly excellent moldability and surface smoothness when used as a container; therefore, the HLMFR (JIS K6922-1) is preferably 3.0 to 60 g / 10 min, and more preferably 5.0 to 50 g / 10 min.

[0022] Since the polyethylene resin produces a container with a particularly small number of fine particles leaching out, it is preferable that the molecular weight distribution curve obtained using GPC contains 0.15% by weight or less of components with a molecular weight of 500 or less, and more preferably 0.10% by weight or less.

[0023] Since the polyethylene resin produces containers with particularly low metal leaching, it is preferable that the amount of metal contained is 10 PPM or less relative to the polyethylene resin. The amount of metal contained is expressed as the ratio of the metal content to the total resin in weight PPM, and the amount of metal contained is obtained by alkali dissolution after ashing the resin, and refers to residual substances such as Mg, Al, and Ti.

[0024] Since the polyethylene resin provides a container with particularly excellent chemical resistance, it is preferable that the ESCR (Electrochemical Storage Criteria) be 50 hours or more.

[0025] The polyethylene resin can be produced using a highly active catalyst such as a Ziegler catalyst or a metallocene catalyst. For example, it can be suitably produced by copolymerizing ethylene or ethylene with α-olefins having 3 to 20 carbon atoms in a ratio that achieves a desired density, using a highly active Ziegler catalyst consisting of transition metal compounds such as titanium and zirconium, magnesium compounds, and organoaluminum compounds as a polymerization catalyst.

[0026] Examples of catalysts include the catalyst described in Japanese Patent No. 3319051.

[0027] As the α-olefins having 3 to 20 carbon atoms, 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, 1-eicosene, etc. can be mentioned.

[0028] In the polymerization method for producing the polyethylene resin, in order to keep the concentration of metal impurities eluted in the chemical low and also limit the incorporation of low molecular weight polymers that cause the generation of fine particles into the resin, slurry polymerization using a polymerization solvent having 6 to 10 carbon atoms, for example, normal hexane, normal heptane, etc. is used, and the MFR is 10 to 30 g / 10 min and the density is 0.960 to 0.970 g / cm ３ of a low molecular weight ethylene-based polymer and HLMFR of 0.005 to 5 g / 10 min and density of 0.920 to 0.940 g / cm ３ It consists of two components of a high molecular weight ethylene-based polymer, and it is preferable that the weight ratio of the two components is 40:60 to 60:40. The two components of the low molecular weight component and the high molecular weight component can be produced, for example, by a two-stage polymerization method.

[0029] Further, since the polyethylene resin becomes a container with few metal contaminants, it is preferable that it does not contain all additives such as antioxidants, light stabilizers, and neutralizing agents.

[0030] The container can be made into a container by using a polyethylene resin having specific properties and molding it into a container shape by blow molding. In particular, a blow molding method using a direct blow molding machine installed in a clean room and using air from which fine particles have been removed by a filter as blow air is preferable for manufacturing a highly clean container.

[0031] The container can be used for semiconductor cleaning chemicals as the content.

[0032] Here, semiconductor cleaning chemicals refer to chemicals with low particulate and metal content used in wafer cleaning processes, etching processes, etc. in the semiconductor manufacturing process. Examples of types of high-purity chemicals include ultrapure water, hydrogen peroxide solution, sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, ammonia water, CMP slurry, photoresist solution, etc.

[0033] Examples of containers include gallon containers, 20 L cans, 200 L plastic drums, etc.

[0034] The shape of the container may be any shape as long as it can store and preserve high-purity chemicals. Examples of containers include cylindrical containers, box-shaped containers, etc.

[0035] The container may be a single-layer container made of polyethylene resin alone, a multi-layer container in which different polyethylene resins are laminated, or a multi-layer container in which a polyethylene resin and a resin other than polyethylene resin are laminated. For example, in order to reinforce the barrier property of high-purity chemicals and the strength of the container, the inner layer is made of one or more resins selected from polyethylene resin, ethylene-vinyl alcohol copolymer, polyvinyl alcohol resin, polyamide resin, and recycled polyethylene resin, and the outer layer is a multi-layer container reinforced with a polyethylene resin having drop impact resistance or FRP, etc., may be used.

[0036] One aspect of the present invention is a method of forming a container by blow molding a polyethylene resin having the following properties (a) to (c), wherein the temperature of the extruded molten resin (parison) is 170°C to 200°C, and the shear rate of the parison at the die outlet is 30 to 100 s －１ This relates to the method for forming the container according to claim 1, characterized in that it becomes such. (a) The density is 0.940 to 0.965 g / cm ３(b) The melt flow rate (MFR) at a temperature of 190°C and a load of 2.16 kg is 0.03 to 1.5 g / 10 min. (c) The ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) determined by gel permeation chromatography (GPC) is 6.0 to 18. The molten resin (parison) temperature at which the polyethylene resin is extruded during blow molding is preferably in the range of 170 to 200°C, and more preferably in the range of 180 to 190°C, in order to produce a container with a small number of fine particles derived from the polyethylene resin.

[0037] Furthermore, the shear rate of the parison at the die exit when the polyethylene resin is extruded during blow molding is set to 30-100 s in order to achieve excellent surface smoothness when used as a container. －１ It is preferable that it be within the range of [specify range].

[0038] As the polyethylene resin, it is preferable to use the polyethylene resin used for the aforementioned container.

[0039] According to the above manufacturing method, a container can be obtained in which there are fewer particulate components generated on the container surface due to molding temperature and other factors, and the leaching of contaminants such as polyethylene resin leaches and degraded products into the contents is minimized, and the container can be used without washing.

[0040] 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.

[0041] (1) Blow molding Using a direct blow molding machine MSE-50E / 54M-A (manufactured by Tahara Corporation) with a 50 mmΦ extrusion screw, the cylinder temperature was set to 170-200°C, the parison temperature to 170-210°C, and the parison shear rate at the die exit to 30-150 s. －１ The parison was continuously extruded from the die tip by modifying the parameters within the specified range, and a container with an internal volume of 800 mL was formed.

[0042] (2) Number of particulate matter In a cleanroom at 23°C, an unwashed or washed container with an internal volume of 800 mL, obtained by blow molding, was filled to 80% of its internal volume with ultrapure water so that the Reynolds number (Re) of the liquid at the time of filling was 2200 ≤ Re ≤ 3200. The container was then sealed and stored for 35 days in a clean oven (Yamato Scientific Co., Ltd., DE411) at a set temperature of 40°C. The number of particulate matter particles larger than 20 nm in the filled water was measured using a particle counter (Rion Co., Ltd., controller: KE-40B1, particle sensor: KS-20F). The number of particulate matter particles in water is expressed as particles / mL.

[0043] (3) Metal elution amount An unwashed container with an internal volume of 800 mL, obtained by blow molding in a clean room at 23°C, was filled to the brim with ultrapure water, sealed, and stored for 7 days. The amount of metal eluted into the filled water was measured using an inductively coupled plasma mass spectrometer (PerkinElmer, ELAN DRCII). The amount of metal eluted into the filled water is shown in PPT.

[0044] (4) Maximum roughness Rz of the inner surface of the container The maximum roughness Rz value of the inner surface of the container body was measured using a shape measuring laser microscope (VK-X200, manufactured by Keyence Corporation).

[0045] (5) Arithmetic mean roughness Ra of the inner surface of the container The arithmetic mean roughness Ra value of the inner surface of the container body was measured using a shape measuring laser microscope (VK-X200, manufactured by Keyence Corporation).

[0046] (6) Density was measured using the density gradient pipe method in accordance with JIS K6922-1.

[0047] (7) MFR was measured in accordance with JIS K6922-1 at 190°C and with a load of 2.16 kg.

[0048] (8) Mw / Mn was measured by GPC using Tosoh HLC-8321GPC / HT (column: Tosoh TSKgel guardcolumnHHR and TSKgelGMHHR-H) with 1,2,4-trichlorobenzene as the eluent. The molecular weight calibration curve was calibrated using polystyrene samples with known molecular weights. (9) HLMFR was measured in accordance with JIS K6922-1 at 190°C and a load of 21.6 kg.

[0049] (10) Components with a molecular weight of 500 or less The proportion of the integrated amount of components with a molecular weight of 500 or less was calculated from the molecular weight distribution curve obtained by GPC measurement.

[0050] (11) Catalyst Residue Amount: After ashing of polyethylene resin, alkali fusion was performed to obtain a solution, which was used as the measurement solution, and the metal content in the sample was measured by ICP-AES measurement.

[0051] (12) Environmental stress crack resistance (ESCR) In accordance with JIS K6922-2, the test specimen was immersed in a nonionic surfactant (10 wt% aqueous solution) at a temperature of 50°C, and the time at which the test specimen cracked with a 50% probability (F50 value) was measured.

[0052] Example 1 <Preparation of Solid Catalyst Component A> 30.0 g (1.23 mol) of metallic magnesium powder and 168.0 g (0.494 mol) of titanium tetrabutoxide were placed in a 3 L glass flask equipped with a stirring device. 192 g (2.59 mol) of n-butanol in which 1.5 g of iodine was dissolved was added over 2 hours at 90°C, and the mixture was stirred at 140°C for 2 hours under a nitrogen seal while removing the generated hydrogen gas. After lowering the temperature 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. Then, 2.1 liters of hexane were added to obtain a homogeneous solution.

[0053] This homogeneous solution was placed in a 10 L stainless steel autoclave equipped with a stirring device. Maintaining the autoclave's internal temperature at 45°C, 800 mL of hexane solution containing 1.0 mol / L of diethylaluminum chloride and 0.5 mol / L of i-butylaluminum dichloride was added over 1 hour, and the mixture was stirred at 60°C for another 1 hour to generate particles. After returning the temperature to 45°C, 1.04 kg (3.35 mol / L) of 50% hexane solution was added over 2 hours. After all the components had been added, the mixture was stirred at 60°C for 1 hour to obtain solid catalyst component A. The obtained solid catalyst component A was used as a hexane slurry in the production of polyethylene A after removing any remaining unreacted materials and by-products using hexane. <Production of Polyethylene A> In the first stage of a continuous polymerization reactor with an internal volume of 370 L, 110 L / hour of dehydrated and purified hexane, 110 mmol / L of tributylaluminum as an organoaluminum compound, 0.4 g / hour of solid catalyst components, 25.4 kg / hour of ethylene, and hydrogen are supplied at a concentration ratio of 0.30 mol / mol to ethylene, while maintaining a temperature of 85°C and a total pressure of 30 kg / cm². ２ Under conditions of an average residence time of 3.4 hours, the first stage of ethylene polymerization (low molecular weight component) was carried out continuously.

[0054] The hexane slurry containing the first-stage polymer was introduced into a 545 L second-stage polymerizer after removing unreacted hydrogen and ethylene in a flash tank. While supplying an additional 45 L / hour of hexane to this polymerizer, ethylene was supplied at 21.5 kg / hour, 1-butene at 2.5 kg / hour, and hydrogen at a concentration ratio of 0.020 mol / mol relative to ethylene, at a temperature of 80°C and a total pressure of 20 kPa / cm². ２ Under conditions of an average residence time of 3.3 hours, ethylene polymerization (high molecular weight component) was carried out. The discharge from the second-stage polymerizer was flushed in a flash tank to remove unreacted hydrogen, ethylene, and 1-butene, washed with hexane at 50 L / hour, and then dried to obtain a mixed powder of ethylene copolymers. The proportion of low molecular weight components was 45% by weight, and the proportion of high molecular weight components was 55% by weight. The powder polymerized in the above two-stage process was pelletized without the addition of additives to obtain polyethylene A. The results of the physical property measurements are shown in Table 1.

[0055] Using polyethylene A, blow molding was performed with a cylinder temperature of 180°C, a parison temperature of 182-183°C, and a parison shear rate of 35-60 s at the die exit. －１ An 800 mL container was molded within the specified range, and the number of fine particles larger than 20 nm and the amount of metal leached from the resulting unwashed container were measured. The results are shown in Table 1.

[0056] Example 2: Using polyethylene A, blow molding was performed with a cylinder temperature of 185°C, a parison temperature of 191-192°C, and a parison shear rate of 70-95 s at the die exit. －１ An 800 mL container was molded within the specified range, and the number of fine particles larger than 20 nm and the amount of metal leached from the resulting unwashed container were measured. The results are shown in Table 1. Example 3 Using polyethylene A, blow molding was performed with a cylinder temperature of 200°C, a parison temperature of 208-209°C, and a parison shear rate of 70-95 s at the die exit. －１ An 800 mL container was molded within the specified range, and after washing the inside of the container with ultrapure water, the number of fine particles larger than 20 nm and the amount of metal leached from the container were measured. The results are shown in Table 1.

[0057] Example 4 <Preparation of Solid Catalyst Component B> 40.0 g (1.65 mol) of metallic magnesium powder and 224 g (0.66 mol) of titanium tetrabutoxide were added to a 3 L glass flask equipped with a stirrer. A mixture of 108 g (1.8 mol) of i-propanol dissolved in 2.0 g of iodine and 135 g (1.8 mol) of n-butanol was placed in a dropping funnel. This mixture was added dropwise to the 3 L flask over 2 hours at a temperature range of 80-95°C. To complete the reaction, the temperature was further raised to 120°C and stirred for 1 hour. Then 2.1 L of hexane was added to obtain a homogeneous solution. Next, this homogeneous solution was placed in a 10 L stainless steel autoclave equipped with a stirrer, and the internal temperature of the autoclave was maintained at 45°C. 1.32 kg (3.3 mol) of a 30% hexane solution of diethylaluminum chloride was added over 1 hour, and the mixture was further stirred at 60°C for 1 hour. Next, 197 g of methylhydropolysiloxane (viscosity approximately 30 centistokes at 25°C) (3.3 grams of silicon atoms) was added and stirred at 68-70°C for 1 hour. After cooling to 45°C, 2.8 kg (9.1 mol) of a 50% hexane solution of i-butylaluminum dichloride was added over 2 hours. After adding all the components, the mixture was stirred at 70°C for 1 hour to obtain solid catalyst component B. The obtained solid catalyst component B was used to remove any remaining unreacted materials and by-products using hexane, and then used to produce hexane slurry and polyethylene B. <Production of polyethylene B> In the first stage of a 370 L continuous polymerizer, 110 L / hour of dehydrated and purified hexane, 120 mmol / hour of tributylaluminum as an organoaluminum compound, 0.5 g / hour of solid catalyst component B, 25.4 kg / hour of ethylene, and hydrogen were supplied at a concentration ratio of 0.35 mol / mol to ethylene, while maintaining a temperature of 85°C and a total pressure of 30 kg / cm². ２ Under conditions of an average residence time of 3.4 hours, the first stage of ethylene polymerization (low molecular weight component) was carried out continuously.

[0058] The hexane slurry containing the first-stage polymer was introduced into a 545 L second-stage polymerizer after removing unreacted hydrogen and ethylene in a flash tank. While supplying an additional 45 L / hour of hexane to this polymerizer, ethylene was supplied at 18.0 kg / hour, 1-butene at 0.6 kg / hour, and hydrogen at a concentration ratio of 0.014 mol / mol relative to ethylene, at a temperature of 80°C and a total pressure of 20 kPa / cm². ２ Ethylene polymerization (high molecular weight component) was carried out under conditions of an average residence time of 3.3 hours. The discharge from the second polymerizer was flushed in a flash tank to remove unreacted hydrogen, ethylene, and 1-butene, washed with hexane at 50 L / hour, and then dried to obtain a mixed powder of ethylene copolymers. The proportion of low molecular weight components was 49% by weight, and the proportion of high molecular weight components was 51% by weight. The powder polymerized in the above two-stage process was pelletized without the addition of additives to obtain polyethylene B. The results of the physical property measurements are shown in Table 1.

[0059] Using polyethylene B, blow molding was performed with a cylinder temperature of 175°C, a parison temperature of 182-183°C, and a parison shear rate of 60-90 s at the die exit. －１ An 800 mL container was molded within the specified range, and the number of fine particles larger than 20 nm and the amount of metal leached from the resulting unwashed container were measured. The results are shown in Table 1.

[0060] Example 5 <Production of Polyethylene C> Except that the hydrogen supplied to the second stage polymerizer was supplied at an ethylene-to-ethylene concentration ratio of 0.05 mol / mol, the polymerization powder was obtained by copolymerization of ethylene and butene-1 in hexane in the same manner as in Example 4, using a two-stage polymerization method. The two-stage polymerized powder was pelletized without the addition of any additives to obtain polyethylene D. The results of the physical property measurements are shown in Table 1.

[0061] Using polyethylene C, blow molding was performed with a cylinder temperature of 185°C, a parison temperature of 187-188°C, and a parison shear rate of 40-70 s at the die exit. －１ An 800 mL container was molded within the specified range, and the number of fine particles larger than 20 nm and the amount of metal leached from the resulting unwashed container were measured. The results are shown in Table 1.

[0062] Comparative Example 1: Using polyethylene A, blow molding was performed with a cylinder temperature of 200°C, a parison temperature of 208-209°C, and a parison shear rate of 70-95 s at the die exit. －１ An 800 mL container was molded within the specified range, and the number of fine particles larger than 20 nm and the amount of metal leached from the resulting unwashed container were measured. The results are shown in Table 1.

[0063] Comparative Example 2: Using polyethylene C, blow molding was performed with a cylinder temperature of 170°C, a parison temperature of 175-177°C, and a parison shear rate of 115-150 s at the die exit. －１ An 800 mL container was molded within the specified range, and the number of fine particles larger than 20 nm and the amount of metal leached from the resulting unwashed container were measured. The results are shown in Table 1.

[0064] Comparative Example 3 <Production of Polyethylene D> Except that hydrogen was supplied to the first polymerizer at a concentration ratio of 0.28 mol / mol to ethylene, 1-butene was supplied to the second polymerizer at a rate of 0.8 kg / hour and hydrogen at a concentration ratio of 0.012 mol / mol to ethylene, and the proportion of low molecular weight components was 50% by weight and high molecular weight components was 50% by weight, ethylene and butene-1 were copolymerized in hexane in the same manner as in Example 1 to obtain a polymerized powder by a two-stage polymerization method. The two-stage polymerized powder was pelletized without the addition of additives to obtain polyethylene D. The results of the physical property measurement are shown in Table 1.

[0065] Using polyethylene D, blow molding was performed with a cylinder temperature of 185°C, a parison temperature of 191-192°C, and a parison shear rate of 75-100 s at the die exit. －１ An 800 mL container was molded within the specified range, and the number of fine particles larger than 20 nm and the amount of metal leached from the resulting unwashed container were measured. The results are shown in Table 1.

[0066] Comparative Example 4 <Production of Polyethylene E> Except that hydrogen was supplied to the first polymerizer at a concentration ratio of 0.45 mol / mol to ethylene, 1-butene was supplied to the second polymerizer at a rate of 1.9 kg / hour and hydrogen at a concentration ratio of 0.016 mol / mol to ethylene, and the proportion of low molecular weight components was 55% by weight and the proportion of high molecular weight components was 45% by weight, ethylene and butene-1 were copolymerized in hexane in the same manner as in Example 1 to obtain a polymerized powder by a two-stage polymerization method. The two-stage polymerized powder was pelletized without the addition of additives to obtain polyethylene E. The results of the physical property measurement are shown in Table 1.

[0067] Using polyethylene E, blow molding was performed with a cylinder temperature of 200°C, a parison temperature of 204-206°C, and a parison shear rate of 50-65 s at the die exit. －１ An 800 mL container was molded within the specified range, and the number of fine particles larger than 20 nm and the amount of metal leached from the resulting unwashed container were measured. The results are shown in Table 1.

[0068] Comparative Example 5 <Production of Polyethylene F> The following commercially available high-density polyethylene was used as polyethylene F.

[0069] Tosoh Corporation, (product name) Nipolon Hard (registered trademark) 8300A (density = 0.955 g / cm³) ３ (MFR = 0.35 g / 10 min) Using polyethylene F, blow molding was performed with a cylinder temperature of 180°C, a parison temperature of 185-186°C, and a parison shear rate of 60-90 s at the die exit. －１ An 800 mL container was molded within the specified range, and the number of fine particles larger than 20 nm and the amount of metal leached from the resulting unwashed container were measured. The results are shown in Table 1.

[0070] Comparative Example 6 <Production of Polyethylene G> The following commercially available high-density polyethylene was used as polyethylene G.

[0071] Manufactured by Tosoh Corporation, (product name) Nipolon Hard (registered trademark) 4030 (density = 0.965 g / cm³) ３ (MFR = 5.0 g / 10 min) Using polyethylene G, blow molding was performed with a cylinder temperature of 180°C, a parison temperature of 185-186°C, and a parison shear rate of 70-100 s at the die exit.－１ An 800 mL container was molded within the specified range, and the number of fine particles larger than 20 nm and the amount of metal leached from the resulting unwashed container were measured. The results are shown in Table 1.

[0072]

[0073] Furthermore, the entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2024-221944, filed on December 18, 2024, are incorporated herein by reference as disclosure of the present invention.

Claims

1. A container made of polyethylene resin that satisfies the following characteristics (1) to (4): (1) The number of fine particles 20 nm or larger that leach from the container after filling it with ultrapure water and storing it at 40°C for 35 days is 40 particles / mL or less. (2) The amount of metal leached from the container after filling it with ultrapure water and storing it at 23°C for 7 days is 30 PPT or less. (3) The maximum roughness Rz of the inner surface of the container is 15.0 μm or less. (4) The arithmetic mean roughness Ra of the inner surface of the container is 1.5 μm or less.

2. The container according to claim 1, wherein the polyethylene resin has the following properties (a) to (c): (a) Density of 0.940 to 0.965 g / cm³ ３ (b) Melt flow rate (MFR) of 0.03 to 1.5 g / 10 min at a temperature of 190°C and a load of 2.16 kg (c) Ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) determined by gel permeation chromatography (GPC) of 6.0 to 18 3. The container according to claim 2, wherein the polyethylene resin has the following properties (d) to (g): (d) Melt flow rate (HLMFR) at a temperature of 190°C and a load of 21.6 kg is 3.0 to 60 g / 10 min (e) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 500 or less is 0.15% by weight or less (f) Metal content is 10 PPM or less relative to the polyethylene resin (g) Environmental stress crack resistance (ESCR) is 50 hours or more 4. A method for forming a container by blow molding a polyethylene resin having the following properties (a) to (c), wherein the temperature of the extruded molten resin (parison) is 170°C to 200°C, and the shear rate of the parison at the die exit is 30 to 100 s. －１ The method for molding a container according to claim 1, characterized in that it is as follows. (a) Density of 0.940–0.965 g / cm³ ３ (b) Melt flow rate (MFR) of 0.03 to 1.5 g / 10 min at a temperature of 190°C and a load of 2.16 kg (c) Ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) determined by gel permeation chromatography (GPC) of 6.0 to 18 5. The method for molding a container according to claim 4, wherein the polyethylene resin has the following properties (d) to (g): (d) Melt flow rate (HLMFR) at a temperature of 190°C and a load of 21.6 kg is 3.0 to 60 g / 10 min (e) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 500 or less is 0.15% by weight or less (f) Metal content is 10 PPM or less relative to the polyethylene resin (g) Environmental stress crack resistance (ESCR) is 50 hours or more

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