JP2023149524A - Polyethylene resin for high purity chemical and container made of the same - Google Patents

Abstract

To provide a polyethylene resin for a high purity chemical container which suppresses elusion of a contaminant such as an eluted matter and a deteriorating matter of a polyethylene resin as much as possible, when the resin is used as a high purity chemical container, and is excellent in chemical resistance, and a container made of the same.SOLUTION: A polyethylene resin for a high purity chemical container contains two components of an ethylene-based polymer having an MFR of 10-40 g/10 min and density of 0.960-0.970 g/cm3 and an ethylene-based polymer having an HLMFR of 0.01-3 g/10 min and density of 0.920-0.940 g/cm3, has a weight ratio of the two components of 40:60 to 60:40, and has specific properties.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a polyethylene resin container for high-purity chemicals and a container made of the same.

In recent years, with the remarkable development of the electronics industry, the demand for high-purity chemicals has increased. High-purity chemicals are used, for example, as essential chemicals in the manufacture of large-scale, integrated electronic circuits such as LSIs. Specifically, sulfuric acid, hydrochloric acid, nitric acid, and hydrogen fluoride are used for wafer cleaning/etching, wiring/insulating film etching, jig cleaning, developing solution, resist diluting solution, resist stripping solution, drying, etc. 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), NMP (N-methyl-2-pyrrolidone) and the like are used. Polyethylene resin is used as the material for these high-purity chemical containers. As the degree of integration of semiconductor circuits increases, the requirements for reducing impurities and particulates in these chemicals have become even more stringent. is also increasing year by year. In addition to the above requirements, there are also increasing demands for larger containers for filling these chemicals, chemical resistance, and the like.

As a way to solve this problem, we have proposed a container that suppresses the amount of hydrocarbon solvent extraction from polyethylene resin and the content of low-molecular components, and limits the amount of antioxidants, neutralizers, and light stabilizers added as much as possible. However, there is insufficient improvement in the effects of ash content caused by catalyst components remaining in polyethylene resin, and countermeasures against the concentration of metal impurities eluted into chemicals have not yet been completed. Further, the level of fine particles is 0.2 μm or more, which is not sufficient (see Patent Documents 1 and 2).

In addition, the density is 0.950 to 0.965 g/cm ³ , the temperature is 190°C, the melt flow rate is 5 to 20 g/10 minutes at a load of 21.6 kg, the constant strain ESCR is 40 hours or more, and the ash content is 20 mass PPM or less. Polyethylene for high-purity chemical containers and high-purity chemical containers have been proposed that have excellent moldability and ESCR properties, but ESCR, which is an indicator of chemical resistance, has been proposed for large 1000L containers (Intermediate Bulk Containers: IBC). ), and the level of fine particles is also insufficient at 0.2 μm or more (see Patent Document 3).

Furthermore, the density is 0.940 to 0.970 g/cm ³ , the temperature is 190°C, and the melt flow rate is 2 to 8.5 g/10 minutes at a load of 21.6 kg, which is determined by gel permeation chromatography (GPC). The ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw/Mn) is 8 to 15, 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, ESCR Although polyethylene resins for ultra-high purity chemical containers and high-purity chemical containers having a property of 130 hours or more have been proposed, 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 Application Publication No. 2018-172177 Patent No. 6705157

The present invention is a polyethylene resin for high-purity chemical containers, and when the polyethylene resin is used as a high-purity chemical container, the elution of contaminants such as eluted substances and degraded substances from the resin is minimized, and chemical resistance is achieved. The object of the present invention is to provide a high-purity polyethylene resin for chemical containers with excellent properties, and a container made of the same.

As a result of intensive studies to solve the above problems, the present inventors have identified properties such as density, melt flow rate, molecular weight determined by gel permeation chromatography (GPC), ESCR, metal content, etc. We have discovered that by using polyethylene having the following properties, it is possible to obtain a high-purity chemical container with less polyethylene-derived fine particles and metal impurities derived from polymerization catalyst components and excellent chemical resistance, and have developed the present invention. Ta.

That is, each aspect of the present invention is [1] to [4] shown below.
[1] An ethylene polymer having a melt flow rate (MFR) of 10 to 40 g/10 minutes at 190°C and a load of 2.16 kg and a density (JIS K6922-1) of 0.960 to 0.970 g/cm ³ , contains two components of 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/cm ³ . A high-purity polyethylene resin for chemical containers having a weight ratio of two components of 40:60 to 60:40 and having the following properties (1) to (9).
(1) Density is 0.940-0.955g/ ^cm3
(2) HLMFR is 1 to 15 g/10 minutes (3) Ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw/Mn) determined by gel permeation chromatography (GPC) is 8 to 15
(4) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 1,000 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 cracking resistance (ESCR) of 1000 hours or more (7) The number of short chain branches with 4 or less carbon atoms per 1000 C of carbon atoms determined by ¹³ C-NMR measurement is 3 or more (8) Containing metal The amount is 20 PPM or less based on 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] Polyethylene resin for purity chemical containers.
[3] A high-purity chemical container made of the polyethylene resin described in [1] or [2] above.
[4] In [3] above, the number of fine particles of 0.1 μm or more eluted from the content after filling an unwashed container with ultrapure water and storing it at 40°C for 35 days is 20 particles/mL or less. Containers for high-purity chemicals as described.

When using the polyethylene resin for high-purity chemical containers that is one aspect of the present invention, it is possible to mold high-purity chemical containers that have less fine particles derived from the polyethylene resin and metal impurities derived from the polymerization catalyst component and have excellent chemical resistance. I can do it. In addition, it is possible to provide a high-purity drug container that is particularly suitable for large containers of 200 L or more, in which the amount of particulate components eluted is small relative to the filled drug, and in which the amount of eluted particulates is small even after long-term storage.

The high-purity polyethylene resin for pharmaceutical use, which is one aspect of the present invention, has a melt flow rate (MFR) of 10 to 40 g/10 minutes at 190°C and a load of 2.16 kg, and a density (JIS K6922-1) of 0.960 to 0. An ethylene polymer with 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/cm ^{3 .} It contains two components of a certain ethylene polymer, the weight ratio of the two components is 40:60 to 60:40, and has the following properties (1) to (9).
(1) Density is 0.940-0.955g/ ^cm3
(2) HLMFR is 1 to 15 g/10 minutes (3) Ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw/Mn) determined by gel permeation chromatography (GPC) is 8 to 15
(4) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 1,000 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 cracking resistance (ESCR) of 1000 hours or more (7) The number of short chain branches with 4 or less carbon atoms per 1000 C of carbon atoms determined by ¹³ C-NMR measurement is 3 or more (8) Containing metal (9) 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 pharmaceutical use is made of Ziegler-based catalysts or metallocene-based catalysts, etc. It can be produced using a highly active catalyst. For example, a highly active Ziegler catalyst consisting of a transition metal compound such as titanium or zirconium, a magnesium compound, and an organoaluminum compound is used as a polymerization catalyst, and ethylene or ethylene and an α-olefin having 3 to 20 carbon atoms are mixed to a desired density. It can be suitably produced by copolymerizing in proportions.
As the catalyst, the catalyst described in Japanese Patent No. 3319051 can be used.

Examples of α-olefins having 3 to 20 carbon atoms include proprene, 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. I can do it.

The polymerization method used to produce this polyethylene resin is to suppress the concentration of metal impurities eluted into chemicals and to limit the incorporation of low-molecular polymers, which cause the generation of fine particles, into the resin. Slurry polymerization using a polymerization solvent of 10 or less, for example, normal hexane, normal heptane, etc., and a low molecular weight ethylene polymer having an MFR of 10 to 40 g/10 minutes and a density of 0.960 to 0.970 g/ ^cm3 . and a high molecular weight ethylene polymer having an HLMFR of 0.01 to 3 g/10 min and a density of 0.920 to 0.940 g/ ^cm3 , and the weight ratio of the two components is 40:60 to 40:60. It is 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.

In addition, the polyethylene resin is specified for 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 metal content as shown below. .

That is, the density (JIS K6922-1) of the polyethylene resin is 0.940 to 0.955 g/cm ³ , preferably 0.945 to 0.949 g/cm ³ . If it is less than 0.940 g/cm ³ , the amount of polymer components eluted into the medicine in the container increases, causing the generation of fine particles. Furthermore, when the density exceeds 0.955 g/cm ³ , the ESCR of the container decreases.

The HLMFR (JIS K6922-1) of the polyethylene resin is 1 to 15 g/10 minutes, preferably 5 to 10 g/10 minutes. If it is less than 1 g/10 minutes, the surface texture of the container will deteriorate. Moreover, when it exceeds 15 g/10 minutes, the ESCR of the container decreases.

The ratio Mw/Mn of Mw and Mn determined by GPC of the polyethylene resin is 8 to 15. If the Mw/Mn is less than 8, the molecular weight distribution will be narrow, the surface texture of the container will deteriorate, and the ESCR of the container will also decrease. When the Mw/Mn exceeds 15, the molecular weight distribution expands, low molecular weight components increase, and the number of fine particles in the container increases. In addition, the shape of the pinch-off portion, which is the parison joining portion, becomes poor, and the drop strength of the container decreases.

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

In the molecular weight distribution curve obtained using GPC of the polyethylene resin, the component having a molecular weight of 100,000 or more is 35% by weight or more. When the component having a molecular weight of 100,000 or more is 35% by weight or more, chemical resistance is excellent. If the content of components with a molecular weight of 100,000 or more is less than 35% by weight, the drop strength of the container will decrease, and the probability of forming a molecular chain (tie molecule) spanning two or more crystals of the polyethylene resin will also decrease, resulting in a decrease in ESCR. do.

The ESCR of the polyethylene resin is 1000 hours or more. When the ESCR is less than 1000 hours, if a container with a capacity larger than 200 L is filled with a chemical, such as a surfactant, and left for six months or more, the container may be damaged due to environmental stress cracking.

The number of single chain branches having 4 or less carbon atoms per 1000 carbon atoms of the polyethylene is 3 or more. When the number of single chain branches is 3 or more, chemical resistance is excellent. When the number of short chain branches is less than three, the probability of forming tie molecules and the ESCR decrease. Moreover, it is preferable that the short chain branch is contained in a high molecular weight ethylene polymer having a molecular weight of 100,000 or more. If the low molecular weight ethylene polymer contains short chain branches, it will elute into the drug and the number of fine particles eluted from the container will increase.

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 eluted into the high-purity drug is small, so the concentration of metal impurities in the drug can be suppressed. The amount of metal content indicates the ratio of the metal content to the total resin in weight PPM. The amount of metals contained is obtained by incinerating the resin and then melting it with an alkali, and it is residual materials such as Mg, Al, and Ti.

After immersing the polyethylene in 70% nitric acid at a temperature of 40° C. for 35 days, the Charpy impact strength retention rate is 50% or more compared to before immersion. In general, polyethylene resin is sensitive to nitric acid, so it deteriorates quickly and its strength tends to decrease. If the Charpy impact strength retention rate after immersion at 40° C. for 35 days is 50% or more, it can be used as a container without being damaged even if it is subjected to impact during transportation or the like.

Furthermore, it is preferable that all additives such as antioxidants, light stabilizers, and neutralizing agents are not added to the polyethylene resin. Here, the neutralizing agents are fatty acid metal salts such as calcium stearate and zinc stearate, and hydrotalcites, which dissolve into chemicals and become metal contaminants. It is preferable that there be.

The polyethylene resin is molded into a container shape by blow molding, resulting in a high-purity drug container. In particular, a blow molding method using a blow molding machine installed in a clean room and using air from which fine particles have been removed with a filter as the blow air is preferable for manufacturing clean containers. The shape and capacity of the container are not specified, but in order to strengthen the barrier properties of the contents and the strength of the container, the resin is used for the inner layer, and the resin is made of ethylene-vinyl alcohol copolymer, polyvinyl alcohol resin, polyamide resin, etc. may be used as an intermediate layer, or FRP or the like may be used as an outer layer for reinforcement.

An unwashed container molded using the polyethylene resin is filled with ultrapure water, and the number of fine particles of 0.1 μm or more eluted from the content is preferably 20 particles/mL or less after storage at 40 ° C. for 35 days. . If the number of fine particles of 0.1 μm or more is 20 particles/mL or less, it can support miniaturization of LSI.

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

The present invention will be explained below with reference to examples, but it is not limited to these examples. The test methods used in Examples and Comparative Examples are as follows.

(1) Density Measured by density gradient tube method in accordance with JIS K6922-1.

(2) HLMFR
Measurement was performed at 190°C and a load of 21.6 kg in accordance with JIS K6922-1.

(3) Mw/Mn
It was measured by GPC using Tosoh HLC-8321GPC/HT (columns: Tosoh TSKgel guardcolumnH _HR and TSKgelGMH _HR -H) and 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 ratio 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 resistance (ESCR)
In accordance with JIS K6922-2, a test piece was immersed in a nonionic sea surfactant (10 wt% aqueous solution) at a temperature of 50°C, and the time at which the test piece would break with a 50% probability (F50 value) was measured.

(6) Number of short chain branches per 1000 C of carbon atoms In the NMR spectrum obtained by ¹³ C NMR measurement using Bruker's AVANCE 600, the sum of all peak areas having peak tops at 5 to 50 ppm was set to 1000. The number of short chain branches was calculated from the peak area derived from the methine carbon to which a branch with 2 carbon atoms was bonded and the peak area derived from the methine carbon to which a branch with 4 carbon atoms was bonded.

(7) Amount of metal content After the sample was incinerated, it was melted with alkali, and the resulting solution was used as a measurement solution, and the amount of metal content in the sample was measured by ICP-AES measurement using Optima 8300.

(8) Charpy impact strength A test piece was prepared according to JIS K7111, and the test piece was immersed in 70% nitric acid at a temperature of 40°C for 35 days.
The impact strength of the test piece after immersion was measured at an ambient temperature of 23° C., and the strength retention rate was determined by comparison with the impact strength value before immersion. Those whose strength retention was 50% or more were rated "○", and those whose strength retention was 50% or less were rated "x".

(9) Blow molding Using a blow molding machine MSE-50E/54M-A (manufactured by Tahara Co., Ltd.) with an extrusion screw of 50 mmΦ, 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. The parison was continuously extruded to form a container with an average wall thickness of 1 mm and an internal volume of 800 mL.

(10) Number of fine particles A container with an internal volume of 800 mL obtained by blow molding a polyethylene resin composition was used. Fill an unwashed container with 600 mL of ultrapure water in a clean room at 23 °C, shake it 15 times with a lid on, and place it in a clean oven (manufactured by Yamato Scientific Co., Ltd., DE411) with a set temperature of 40 °C. After being stored for 35 days, the number of particles of 0.1 μm or more 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 fine particles in water is expressed in particles/mL.

Example 1
<Manufacture of polyethylene A>
In the first stage of a continuous polymerization vessel with an internal volume of 370 L, dehydrated and purified hexane was used at 110 L/hour, triisobutylaluminum was used as an organoaluminum compound at 110 mmoL/hour, and Mg, Al, and Ti prepared according to JP-A-7-41513 were used. While supplying 0.70 g/hour of Ziegler solid catalyst component mainly composed of Cl, 24.0 kg/hour of ethylene, and 0.50 moL/moL of hydrogen at a concentration ratio of ethylene to ethylene, the temperature was 85%. The first stage of ethylene polymerization (low molecular weight component) was carried out continuously under the following conditions: °C, total pressure of 30 kg/cm ² and average residence time of 3.4 hours. The MFR of the low molecular weight component was 20 g/10 min, and the density was 0.970 g/cm ³ .

The hexane slurry containing the first-stage polymer was introduced into a second-stage polymerization vessel having an internal volume of 545 L after removing unreacted hydrogen and ethylene in a flash tank. While supplying an additional 45 L/hour of hexane to this polymerization reactor, ethylene was added at a rate of 24.0 kg/hour, 1-butene was added at a rate of 8.1 kg/hour, and hydrogen was added at a concentration ratio of 0.020 moL/moL to ethylene. Ethylene polymerization (high molecular weight component) was carried out under the conditions of a temperature of 80° C., a total pressure of 20 kPa/cm ² and an average residence time of 3.3 hours while supplying the solution. The HLMFR of the high molecular weight component was 0.10 g/10 min, and the density was 0.925 g/cm ³ . The discharged material from the second stage polymerization vessel is sent to a flash tank to remove unreacted hydrogen, ethylene, and 1-butene, washed with 50 L/hour of hexane, and then subjected to a drying process to form an ethylene copolymer. A mixture powder was obtained. 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 subjected to two-stage polymerization in the above production process was pelletized without the addition of any additives to obtain polyethylene A. Table 1 shows the physical property measurement results.

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

Example 2
<Manufacture of polyethylene B>
Ethylene and butene-1 were prepared in hexane in the same manner as in Example 1, except that 1-butene was supplied to the second stage polymerizer at a rate of 8.5 kg/hour and hydrogen was supplied at a concentration ratio of 0.025 moL/moL to ethylene. Copolymerization was performed to obtain a polymer powder by a two-stage polymerization method. The HLMFR of the high molecular weight component in the second stage polymerization vessel was 0.05 g/10 min, and the density was 0.922 g/cm ³ . The two-stage polymerized powder was pelletized without adding any additives to obtain polyethylene B. Table 1 shows the physical property measurement results.

Polyethylene B was blow-molded, and the above-described fine particle measurement was performed using the resulting container. 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/cm ³ )
Polyethylene C was blow molded in the same manner as in the example, and the number of fine particles was measured. Table 1 shows the physical properties of the resin and the evaluation results of the container.

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

Manufactured by Tosoh Corporation, (trade name) Nipolon Hard 8D01A (HLMFR = 8.0 g/10 min, density = 0.957 g/cm ³ )
Polyethylene D was blow molded and the number of fine particles was measured. Table 1 shows the physical properties of the resin and the evaluation results of the container.

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

Manufactured by Tosoh Corporation, (trade name) Nipolon Hard 8022 (HLMFR = 25 g/10 min, density = 0.958 g/cm ³ )
Polyethylene E was blow molded and the number of fine particles was measured. Table 1 shows the physical properties of the resin and the evaluation results of the container.

Comparative example 4
<Preparation of solid catalyst component> 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-liter glass flask equipped with a stirring device, and 1.5 g of iodine was added. 192 g (2.59 mol) of n-butanol dissolved therein was added at 90° C. over 2 hours, and the mixture was further stirred at 140° C. for 2 hours under a nitrogen blanket while excluding generated hydrogen gas. After bringing 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 further stirred at 140°C for 2 hours. Then, 2.1 liters of hexane was added to obtain a homogeneous solution. This homogeneous solution was placed in a 10 liter stainless steel autoclave equipped with a stirring device, and while the internal temperature of the autoclave was maintained at 45°C, 800 ml of a hexane solution containing 1.0 mol of diethyl aluminum chloride and 0.5 mol of i-butyl aluminum dichloride was added. The mixture was added over 1 hour and further stirred at 60°C for 1 hour to generate particles. After raising the temperature to 45° C. again, 1.04 kg (3.35 mol) of 50% hexane solution was added over 2 hours. After everything was added, stirring was performed at 60° C. for 1 hour to obtain a solid catalyst component. The obtained solid catalyst component was used in the production of polyethylene F as a hexane slurry after removing remaining unreacted substances and by-products using hexane.

<Manufacture of polyethylene F> In the first stage of a continuous polymerization vessel with an internal volume of 370 L, dehydrated and purified hexane was fed at 110 L/hour, triisobutylaluminum was fed as an organic aluminum compound at 110 mmol/hour, and the above solid catalyst component was fed at 0.4 g/hour. While supplying ethylene at 25.4 kg/hour and hydrogen at a concentration ratio of 0.28 moL/moL to ethylene, the temperature was 85°C, the total pressure was 30 kg/cm ² , and the average residence time was 3.4 hours. The first stage (low molecular weight component) was continuously polymerized under the following conditions. The MFR of the low molecular weight component was 16 g/10 min, and the density was 0.974 g/cm ³ .

After removing unreacted hydrogen and ethylene from the hexane slurry containing the first-stage polymer in a flash tank, it was introduced into another continuous polymerization vessel having an internal volume of 545 liters. While supplying an additional 45 L/hour of hexane to this polymerization vessel, ethylene was fed at 21.5 kg/hour, 1-butene at 0.8 kg/hour, hydrogen at a concentration ratio of 0.12 moL/moL to ethylene, temperature 80°C, total The second stage (high molecular weight component) was polymerized under the conditions of a pressure of 20 kg/cm ² and an average residence time of 3.3 hours. The density of the high molecular weight component was 0.940 g/cm ³ . After removing unreacted hydrogen, ethylene, and 1-butene from the discharge from the second-stage polymerization vessel in a flash tank, it was washed with 50 L/hour of hexane, and then subjected to a drying process to produce an ethylene copolymer. Obtained. The proportion of low molecular weight components was 50% by weight, and the proportion of high molecular weight components was 50% by weight. The powder subjected to two-stage polymerization in the above production process was pelletized without the addition of any additives to obtain polyethylene F. Table 1 shows the physical property measurement results.

Polyethylene F was blow molded and the number of fine particles was measured. Table 1 shows the physical properties of the resin and the evaluation results of the container.

Claims (4)

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/cm ³ and 190°C. , contains two components of an ethylene polymer having a melt flow rate (HLMFR) of 0.01 to 3 g/10 min at a load of 21.6 kg and a density of 0.920 to 0.940 g/ ^cm3 , and of the two components. A high-purity polyethylene resin for chemical containers having a weight ratio of 40:60 to 60:40 and having the following properties (1) to (9).
(1) Density is 0.940-0.955g/ ^cm3
(2) HLMFR is 1 to 15 g/10 minutes (3) Ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw/Mn) determined by gel permeation chromatography (GPC) is 8 to 15
(4) In the molecular weight distribution curve obtained using GPC, the component with a molecular weight of 1,000 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 cracking resistance (ESCR) of 1000 hours or more (7) The number of short chain branches with 4 or less carbon atoms per 1000 C of carbon atoms determined by ¹³ C-NMR measurement is 3 or more (8) Containing metal (9) Charpy impact strength retention rate after immersion in 70% nitric acid at 40°C for 35 days is 50% or more The polyethylene resin for high purity chemical containers according to claim 1, which does not contain additives. A high purity chemical container made of the polyethylene resin according to claim 1 or 2. The high purity according to claim 3, wherein the number of fine particles of 0.1 μm or more eluted from the content after filling an unwashed container with ultrapure water and storing it at 40° C. for 35 days is 20 particles/mL or less. Container for medicine.