JP7844991B2 - High-purity polyethylene resin for chemical use and containers made thereof - Google Patents

Description

This invention relates to polyethylene resin containers for high-purity chemicals and containers made therefrom.

In recent years, with the remarkable development of the electronics industry, the demand for high-purity chemicals has increased. High-purity 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. Polyethylene resin is used as the container material for these high-purity chemicals. As the integration density of semiconductor circuits improves, the demand for reducing impurities and fine particles in these chemicals has become increasingly stringent, and in order to satisfy these stringent requirements, the demand for cleanliness in the containers that fill these chemicals has also increased year by year. In addition to the above requirements, there is also a growing demand for larger containers and greater chemical resistance for these chemicals.

To address this problem, a proposed container design minimizes the amount of hydrocarbon solvents extracted from polyethylene resin, reduces the content of low-molecular-weight components, and restricts the addition of antioxidants, neutralizing agents, and lightfastness agents. However, improvements to address the 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. Furthermore, the particle size is insufficient at 0.2 μm or larger (see Patent Documents 1 and 2).

Furthermore, high-purity polyethylene for chemical containers and high-purity chemical containers have been proposed that exhibit excellent moldability and ESCR, having properties such as a density of 0.950 to 0.965 g/ ^cm³ , a melt flow rate of 5 to 20 g/10 min at a temperature of 190°C and a 21.6 kg load, a constant strain ESCR of 40 hours or more, and an ash content of 20 mass PPM or less. However, the ESCR, which is an indicator of chemical resistance, is insufficient for large 1000 L containers (Intermediate Bulk Containers: IBCs), and the level of fine particles is also insufficient at 0.2 μm or larger (see Patent Document 3).

Furthermore, ultra-high-purity polyethylene resins and high-purity chemical containers have been proposed that have properties such as a density of 0.940 to 0.970 g/ ^cm³ , a melt flow rate of 2 to 8.5 g/10 min at a temperature of 190°C and a 21.6 kg load, a ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw/Mn) of 8 to 15 determined by gel permeation chromatography (GPC), a molecular weight distribution curve obtained using GPC showing that components with a molecular weight of 1000 or less account for 0.30% by weight or less, and an ESCR of 130 hours or more. However, the ESCR was insufficient for IBC containers (see Patent Document 4).

Japanese Patent Application Publication No. 7-62161 Japanese Patent Application Publication No. 7-257540 Japanese Patent Publication No. 2018-172177 Patent No. 6705157

The present invention aims to provide a polyethylene resin for high-purity chemical containers that, when used as a high-purity chemical container, minimizes the leaching of contaminants such as leached substances and degraded substances from the resin, and offers excellent chemical resistance, as well as a container made therefrom.

The inventors of this invention, after diligent research to solve the above problems, discovered that by using polyethylene with specific properties such as density, melt flow rate, molecular weight determined by gel permeation chromatography (GPC), ESCR, and metal content, it is possible to obtain high-purity chemical containers with low levels of polyethylene-derived fine particles and metal impurities derived from polymerization catalyst components, as well as excellent chemical resistance. This led to the development of the present invention.

In other words, the embodiments of the present invention are as follows: [1] to [4].
[1] A high-purity polyethylene resin for chemical containers comprising two components: an ethylene polymer having a melt flow rate (MFR) of 10 to 40 g/ ¹⁰ min at 190°C and a load of 2.16 kg, and a density (JIS K6922-1) of 0.960 to 0.970 g/ ^cm³ ; and an ethylene polymer having a melt flow rate (HLMFR) of 0.01 to 3 g/10 min at 190°C and a load of 21.6 kg, and a density of 0.920 to 0.940 g/cm³, wherein the weight ratio of the two components is 40:60 to 60:40, and having the following properties (1) to (9).
(1) Density of 0.940–0.955 g/ ^cm³
(2) HLMFR is 1-15 g/10 min (3) Ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw/Mn) determined by gel permeation chromatography (GPC) is 8-15
(4) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 1000 or less is 0.30% by weight or less. (5) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 100,000 or more is 35% by weight or more. (6) Environmental stress crack resistance (ESCR) is 1000 hours or more. (7) The number of short chain branches with 4 or fewer carbon atoms per 1000 carbon atoms, as determined by ^13C -NMR measurement, is 3 or more. (8) The amount of metal contained is 20 PPM or less relative to the polyethylene resin. (9) The Charpy impact strength retention rate after immersion in 70% nitric acid at 40°C for 35 days is 50% or more. [2] High-purity polyethylene resin for chemical containers as described in [1] above, free of additives.
[3] A high-purity chemical container made of polyethylene resin as described in [1] or [2] above.
[4] A container for high-purity chemicals as described in [3] above, wherein the number of fine particles 0.1 μm or larger that leach from the contents of an unwashed container filled with ultrapure water after standing storage at 40°C for 35 days is 20 or less per mL.

When using a polyethylene resin for high-purity chemical containers according to one aspect of the present invention, it is possible to mold high-purity chemical containers with excellent chemical resistance, as they contain fewer fine particles derived from the polyethylene resin and fewer metal impurities derived from polymerization catalyst components. Furthermore, it is particularly suitable for large containers of 200L or more, providing high-purity chemical containers that minimize the elution of fine particle components from the filled chemicals and maintain low elution even after long-term storage.

A high-purity polyethylene resin for chemicals, according to one aspect of the present invention, comprises ^two components: an ethylene polymer having a melt flow rate (MFR) of 10 to 40 g/10 min at 190°C and a 2.16 kg load, and a density (JIS K6922-1) of 0.960 to 0.970 g/cm³; and an ethylene polymer having a melt flow rate (HLMFR) of 0.01 to 3 g/10 min at 190°C and a 21.6 kg load, and a density of 0.920 to 0.940 g/cm³ ^. The weight ratio of these two components is 40:60 to 60:40, and it has the following properties (1) to (9).
(1) Density of 0.940–0.955 g/ ^cm³
(2) HLMFR is 1-15 g/10 min (3) Ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw/Mn) determined by gel permeation chromatography (GPC) is 8-15
(4) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 1000 or less is 0.30% by weight or less. (5) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 100,000 or more is 35% by weight or more. (6) Environmental stress crack resistance (ESCR) is 1000 hours or more. (7) The number of short-chain branches with 4 or fewer carbon atoms per 1000 carbon atoms, as determined from ^13C -NMR measurement, is 3 or more. (8) The amount of metal contained is 20 PPM or less relative to the polyethylene resin. (9) The Charpy impact strength retention rate after immersion in 70% nitric acid at 40°C for 35 days is 50% or more. High-purity polyethylene resin for chemical use 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 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, and copolymerizing ethylene or ethylene with α-olefins having 3 to 20 carbon atoms in a ratio that results in a desired density.
Examples of catalysts include the catalyst described in Japanese Patent No. 3319051.

Examples of α-olefins 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.

The polymerization method for producing the polyethylene resin is slurry polymerization using a polymerization solvent with 6 to 10 carbon atoms, such as n-hexane or n-heptane, in order to keep the concentration of metal impurities eluted into the chemical low and to limit the incorporation of low molecular weight polymers into the resin, which can cause the generation of fine particles. The polymer consists of two components: a low molecular weight ethylene polymer with an MFR of 10 to 40 g/10 min and a density of 0.960 to 0.970 g/ ^cm³ , and a high molecular weight ethylene polymer with an HLMFR of 0.01 to 3 g/10 min and a density of 0.920 to 0.940 g/ ^cm³ , with a weight ratio of 40:60 to 60:40. The two components, the low molecular weight component and the high molecular weight component, can be produced, for example, by a two-stage polymerization method.

Furthermore, the polyethylene resin is specified as follows: density, HLMFR, molecular weight distribution (Mw/Mn), components with a molecular weight of 1000 or less, number of short-chain branches per 1000 carbon atoms, ESCR, and amount of contained metal.

Specifically, the density of the polyethylene resin (JIS K6922-1) is 0.940 to 0.955 g/ ^cm³ , preferably 0.945 to 0.949 g/ ^cm³ . If the density is less than 0.940 g/ ^cm³ , the amount of polymer components leached into the chemicals in the container increases, causing the generation of fine particles. Furthermore, if the density exceeds 0.955 g/ ^cm³ , the ESCR of the container decreases.

The HLMFR (JIS K6922-1) of the polyethylene resin is 1 to 15 g/10 min, preferably 5 to 10 g/10 min. Below 1 g/10 min, the surface texture of the container deteriorates. Above 15 g/10 min, the ESCR of the container decreases.

The Mw/Mn ratio of the polyethylene resin, determined by GPC (Gross Propagation Spectroscopy), is between 8 and 15. If Mw/Mn is less than 8, the molecular weight distribution is narrow, resulting in poor surface texture of the container and a decrease in the container's ESCR (Electromagnetic Surcharge Retention). If Mw/Mn exceeds 15, the molecular weight distribution expands, increasing the amount of low-molecular-weight components and the amount of fine particles in the container. Furthermore, the shape of the pinch-off portion, which is the parison bond, deteriorates, reducing the container's drop strength.

In the molecular weight distribution curve obtained using GPC of the polyethylene resin, the component with a molecular weight of 1000 or less is 0.30% by weight or less. If the component with a molecular weight of 1000 or less exceeds 0.30% by weight, the low molecular weight component increases, and the number of fine particles leaching from the container increases.

In the molecular weight distribution curve obtained using GPC of the polyethylene resin, the component with a molecular weight of 100,000 or more accounts for 35% by weight or more. When the component with a molecular weight of 100,000 or more accounts for 35% by weight or more, the chemical resistance is excellent. If the component with a molecular weight of 100,000 or more accounts for less than 35% by weight, the drop strength of the container decreases, and the probability of forming molecular chains (tie molecules) spanning two or more crystals of the polyethylene resin also decreases, resulting in a decrease in ESCR (Electrochemical Stress Corrosion Criticality).

The ESCR (Energy Storage Critical Rate) of the polyethylene resin is 1000 hours or more. If the ESCR is less than 1000 hours, filling a container with a capacity larger than 200 L with chemicals, such as surfactants, and leaving it for more than six months may cause the container to break due to environmental stress cracking.

The polyethylene has three or more single-chain branches with four or fewer carbon atoms per 1000 carbon atoms. Having three or more single-chain branches provides excellent chemical resistance. If the number of short-chain branches is less than three, the probability of tie molecule formation and ESCR decrease. Furthermore, it is preferable that the short-chain branches are included in high molecular weight ethylene polymers with a molecular weight of 100,000 or more. If short-chain branches are included in low molecular weight ethylene polymers, they leach into chemicals, increasing the number of fine particles leached from the container.

The amount of metal contained in the polyethylene resin is 20 PPM or less relative to the polyethylene resin. If the amount of metal contained is 20 PPM or less, the amount of metal leaching into high-purity chemicals is small, thus suppressing the concentration of metal impurities in the chemicals. The amount of metal contained is expressed as the percentage of metal content relative to the total resin, expressed in weight PPM. The amount of metal contained is obtained by alkali dissolution after ashing the resin, and consists of residual substances such as Mg, Al, and Ti.

The Charpy impact strength retention rate of the polyethylene after immersion in 70% nitric acid at 40°C for 35 days is 50% or more compared to before immersion. Generally, polyethylene resin is susceptible to nitric acid, leading to rapid degradation and a decrease in strength. If the Charpy impact strength retention rate after 35 days of immersion at 40°C is 50% or more, the polyethylene can be used as a container without damage even when subjected to impact during transportation.

Furthermore, it is preferable that the polyethylene resin contains no additives whatsoever, including antioxidants, light stabilizers, and neutralizing agents. Here, neutralizing agents refer to fatty acid metal salts such as calcium stearate and zinc stearate, and hydrotalcites, all of which dissolve into the chemical and become metal contaminants; therefore, their absence is preferable.

The polyethylene resin can be molded into containers by blow molding to produce high-purity chemical containers. In particular, a blow molding method using a blow molding machine installed in a cleanroom and using filtered air as the blow air is preferable for producing clean containers. While the container shape and capacity are not specified, to reinforce the barrier properties of the contents and the strength of the container, the resin may be used as the inner layer, and ethylene-vinyl alcohol copolymer, polyvinyl alcohol resin, and polyamide resin may be used as intermediate layers, or FRP may be used as an outer layer for reinforcement.

When an unwashed container molded using the polyethylene resin is filled with ultrapure water, the number of fine particles 0.1 μm or larger that elute the contents is preferably 20 particles/mL or less after storage at 40°C for 35 days. A particle count of 20 particles/mL or less allows for the miniaturization of LSIs.

Examples of containers molded using this polyethylene resin include 1000L containers (Intermediate Bulk Containers: IBCs). Smaller containers include, for example, 200L drums and 20L industrial chemical cans.

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.

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

(2) HLMFR
Measurements were taken in accordance with JIS K6922-1, at 190°C and under a load of 21.6 kg.

(3) Mw/Mn
The molecular weight was measured by GPC using a Tosoh HLC-8321GPC/HT column (Tosoh TSKgel guardcolumnH _HR and TSKgelGMH _HR -H) with 1,2,4-trichlorobenzene as the eluent. The molecular weight calibration curve was calibrated using polystyrene samples with known molecular weights.

(4) Components with molecular weights of 1,000 or less and 100,000 or more The proportion of the integrated amounts of components with molecular weights of 1,000 or less and components with molecular weights of 100,000 or more was calculated from the molecular weight distribution curve obtained by GPC measurement.

(5) Environmental stress cracking (ESCR)
In accordance with JIS K6922-2, test specimens were immersed in a nonionic surfactant (10 wt% aqueous solution) at a temperature of 50°C, and the time at which the test specimen fractured with a 50% probability (F50 value) was measured.

(6) Number of short-chain branches per 1000 carbon atoms Using a Bruker AVANCE600, the number of short-chain branches was calculated from the peak area originating from methine carbons to which branches with ² carbon atoms are bonded, and from the peak area originating from methine carbons to which branches with 4 carbon atoms are bonded, when the sum of all peak areas having peak tops between 5 and 50 ppm in the NMR spectrum obtained by 13C NMR measurement was set to 1000.

(7) Amount of metal contained The sample was ashed and then subjected to alkaline fusion to obtain a solution, which was used as the measurement solution. The amount of metal contained in the sample was measured by ICP-AES measurement using an Optima 8300.

(8) Charpy impact strength Test specimens were prepared in accordance with JIS K7111 and immersed in 70% nitric acid at a temperature of 40°C for 35 days.
The impact strength of the test specimens after immersion was measured at an ambient temperature of 23°C, and the strength retention rate was determined by comparing it with the impact strength value before immersion. Specimens with a strength retention rate of 50% or more were marked with "○", and those with a strength retention rate of 50% or less were marked with "×".

(9) Blow molding Using a blow molding machine MSE-50E/54M-A (manufactured by Tahara Corporation) with a 50 mmΦ extrusion screw, parisons were continuously extruded from the tip of the die at a cylinder temperature of 180 to 190°C and a screw rotation speed of 16 to 18 revolutions per minute to form containers with an average wall thickness of 1 mm and an internal volume of 800 mL.

(10) Number of particulate matter A container with an internal volume of 800 mL obtained by blow molding a polyethylene resin composition was used. 600 mL of ultrapure water was filled into an unwashed container in a clean room at 23°C, the lid was closed and shaken 15 times, and the container was left standing for 35 days in a clean oven (Yamato Scientific Co., Ltd., DE411) at a set temperature of 40°C. The number of particulate matter 0.1 μm or larger in the filled water was measured using a particle counter (Rion Co., Ltd., controller: KE-40B1, particle sensor: KS-42A). The number of particulate matter in the water is expressed as particles/mL.

Example 1
<Manufacturing of Polyethylene A>
In a continuous polymerizer with an internal volume of 370 L, the first stage of ethylene polymerization (low molecular weight component) was carried out continuously under conditions of a temperature of 85°C, a total pressure of 30 kg/cm², and an average residence time of 3.4 hours, while supplying 110 L/hour of dehydrated and purified hexane, 110 mmol/hour of triisobutylaluminum as an organoaluminum compound, 0.70 g/hour of a Ziegler-type solid catalyst component mainly composed of Mg, Al, Ti, and Cl prepared according to Japanese Patent Publication No. ^7-41513 , 24.0 kg/hour of ethylene, and hydrogen at a concentration ratio of 0.50 mol/mol to ethylene. The MFR of the low molecular weight component was 20 g/10 min, and its density was 0.970 g/ ^cm³ .

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. Ethylene polymerization (high molecular weight component) was carried out under conditions of 80°C, a total pressure of 20 kPa/ ^cm² , and an average residence time of 3.3 hours, while supplying ethylene at 24.0 kg/hour, 1-butene at 8.1 kg/hour, and hydrogen at a concentration ratio of 0.020 mol/mol to ethylene. The HLMFR of the high molecular weight component was 0.10 g/10 min, and its density was 0.925 g/ ^cm³ . The discharge from the second-stage polymerizer was removed in a flash tank to remove unreacted hydrogen, ethylene, and 1-butene, washed with 50 L/hour of hexane, and then dried to obtain a mixture powder of ethylene-based copolymers. The proportion of the low molecular weight component was 49% by weight, and the proportion of the high molecular weight component was 51% by weight. The powder polymerized in two stages using the above manufacturing process was pelletized without the addition of any additives to obtain polyethylene A. The results of the physical property measurements are shown in Table 1.

Polyethylene A was blow-molded, and the resulting container was used to perform the fine particle measurement described above. The results are shown in Table 1.

Example 2
<Manufacturing of Polyethylene B>
Polymerized powder was obtained by copolymerizing ethylene and butene-1 in hexane in the same manner as in Example 1, except that 8.5 kg/hour of 1-butene and hydrogen were supplied to the second polymerizer at a concentration ratio of 0.025 mol/mol relative to ethylene. The HLMFR of the high molecular weight component in the second polymerizer was 0.05 g/10 min, and the density was 0.922 g/ ^cm³ . The two-stage polymerized powder was pelletized without the addition of any additives to obtain polyethylene B. The results of the physical property measurements are shown in Table 1.

Polyethylene B was blow-molded, and the resulting container was used to perform the fine particle measurement described above. The results are shown in Table 1.

Comparative Example 1
As polyethylene C, the following commercially available high-density polyethylene was used.

Manufactured by Tosoh Corporation, (product name) Nipolon Hard 8900 (HLMFR = 2.5 g/10 min, density = 0.954 g/ ^cm³ )
Polyethylene C was blow-molded in the same manner as in the examples, and the number of particulate matter was measured. The physical properties of the resin and the evaluation results of the container are shown in Table 1.

Comparative Example 2
As polyethylene D, the following commercially available high-density polyethylene was used.

Tosoh Corporation, (product name) Nipolon Hard 8D01A (HLMFR = 8.0 g/10 min, density = 0.957 g/ ^cm³ )
Polyethylene D was blow-molded, and the number of particulate matter particles was measured. The physical properties of the resin and the evaluation results of the container are shown in Table 1.

Comparative Example 3
As polyethylene E, the following commercially available high-density polyethylene was used.

Tosoh Corporation, (product name) Nipolon Hard 8022 (HLMFR = 25 g/10 min, density = 0.958 g/ ^cm³ )
Polyethylene E was blow-molded, and the number of particulate matter particles was measured. The physical properties of the resin and the evaluation results of the container are shown in Table 1.

Comparative Example 4
<Preparation of Solid Catalyst Components> In a 3-liter glass flask equipped with a stirring device, 30.0 g (1.23 mol) of metallic magnesium powder and 168.0 g (0.494 mol) of titanium tetrabutoxide were placed. 192 g (2.59 mol) of n-butanol in which 1.5 g of iodine had been 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 reducing 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. This homogeneous solution was placed in a 10-liter stainless steel autoclave equipped with a stirring device. The autoclave temperature was maintained at 45°C, and 800 ml of 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 another hour to generate particles. After returning the temperature to 45°C, 1.04 kg (3.35 mol) 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 a solid catalyst component. The obtained solid catalyst component was used as a hexane slurry to produce polyethylene F after removing any remaining unreacted materials and by-products using hexane.

<Production of Polyethylene F> Polymerization of the first stage (low molecular weight component) was carried out continuously in a continuous polymerizer with an internal volume of 370 L, while supplying 110 L/hour of dehydrated and purified hexane, 110 mmol/hour of triisobutylaluminum as an organoaluminum compound, 0.4 g/hour of the above solid catalyst component, 25.4 kg/hour of ethylene, and hydrogen at a concentration ratio of 0.28 mol/mol to ethylene, under conditions of a temperature of 85°C, a total pressure of 30 kg/ ^cm² , and an average residence time of 3.4 hours. The MFR of the low molecular weight component was 16 g/10 min, and the density was 0.974 g/ ^cm³ .

The hexane slurry containing the first-stage polymer was introduced into another continuous polymerizer with an internal volume of 545 liters after removing unreacted hydrogen and ethylene in a flash tank. The second stage (high molecular weight component) polymerization was carried out in this polymerizer under the following conditions: ethylene at 21.5 kg/hour, 1-butene at 0.8 kg/hour, hydrogen at a hydrogen-to-ethylene concentration ratio of 0.12 mol/mol, temperature 80°C, total pressure 20 kg/ ^cm² , and average residence time 3.3 hours, while supplying an additional 45 L/hour of hexane. The density of the high molecular weight component was 0.940 g/ ^cm³ . The waste from the second-stage polymerizer was removed in a flash tank to remove unreacted hydrogen, ethylene, and 1-butene, then washed with 50 L/hour of hexane, followed by a drying process to obtain an ethylene-based copolymer. The proportion of the low molecular weight component was 50% by weight, and the proportion of the high molecular weight component was 50% by weight. The powder polymerized in the two-stage polymerization process described above was pelletized without additives to obtain polyethylene F. The results of the physical property measurements are shown in Table 1.

Polyethylene F was blow-molded, and the number of particulate matter particles was measured. Table 1 shows the physical properties of the resin and the evaluation results for the container.

Claims (4)

A high-purity polyethylene resin for chemical containers comprising ^two components: an ethylene polymer having a melt flow rate (MFR) of 10 to 40 g/10 min at 190°C and a load of 2.16 kg, and a density (JIS K6922-1) of 0.960 to 0.970 g/cm³; and an ethylene polymer having a melt flow rate (HLMFR) of 0.01 to 3 g/10 min at 190° ^C and a load of 21.6 kg, and a density of 0.920 to 0.940 g/cm³, wherein the weight ratio of the two components is 40:60 to 60:40, and having the following properties (1) to (9).
(1) Density of 0.940–0.955 g/ ^cm³
(2) HLMFR is 1-15 g/10 min (3) Ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw/Mn) determined by gel permeation chromatography (GPC) is 8-15
(4) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 1000 or less is 0.30% by weight or less. (5) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 100,000 or more is 35% by weight or more. (6) Environmental stress crack resistance (ESCR) is 1000 hours or more. (7) The number of short-chain branches with 4 or fewer carbon atoms per 1000 carbon atoms, as determined by ^13C -NMR measurement, is 3 or more. (8) The amount of metal contained is 20 PPM or less relative to the polyethylene resin. (9) The Charpy impact strength retention rate after immersion in 70% nitric acid at 40°C for 35 days is 50% or more. A high-purity polyethylene resin for chemical containers according to claim 1, free of additives. A high-purity chemical container made of polyethylene resin according to claim 1 or 2. A high-purity chemical container according to claim 3, wherein the number of fine particles 0.1 μm or larger that elute from the contents of an unwashed container filled with ultrapure water after standing storage at 40°C for 35 days is 20 particles/mL or less.