JP2021195436A - Polyethylene-based resin composition and container for high purity chemical solution - Google Patents

Abstract

To provide a polyethylene-based resin composition which reduces deterioration in a molding surface of a container obtained by blow molding, suppresses elution of fine particles and metal, and is suitable for a container for high purity chemical solution.SOLUTION: A polyethylene-based resin composition contains 99.90-99.99 wt.% of a polyethylene resin satisfying the following requirements (1) to (5) and 0.01-0.10 wt.% of a vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer. (1) Density of 940-960 kg/m3, (2) melt flow rate at 190°C and 21.6 kg load of 2.0-12 g/10 min, (3) ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) of 8.0-15, (4) component having a molecular weight of 1,000 or less of 0.50 wt.% or less, and (5) metal content of 20 ppm or less.SELECTED DRAWING: None

Description

INDUSTRIAL APPLICABILITY The present invention is suitable for manufacturing containers for high-purity chemicals used in the fields of semiconductor equipment industry, precision industrial parts, pharmaceuticals, etc., and particularly when the product has a good skin and is filled with high-purity chemicals. The present invention relates to a polyethylene-based resin composition for high-purity chemicals in which the generation of fine particles and the elution of metals are small.

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 indispensable chemicals for manufacturing electronic circuits such as large-scale and integrated LSIs. Specifically, for wafer cleaning / etching, wiring / insulating film etching, jig cleaning, developing solution, resist diluent, resist stripping solution, drying, etc., sulfuric acid, hydrochloric acid, nitric acid, hydrogen fluoride, etc. Acid, ammonium fluoride, aqueous hydrogen peroxide, isopropyl alcohol, xylene, TMAH (tetramethylammonium hydroxide), methanol, acetic acid, phosphoric acid, aqueous ammonia, PGMEA (propylene glycol methyl ether acetate), DMSO (dimethylsulfoxide), NMP (N-methyl-2-pyrrolidone) and the like are used. Conventionally, polyethylene resin has been used as a container material for these high-purity chemicals in terms of chemical resistance, impact resistance, price and the like. When a container for high-purity chemicals is molded by blow molding, a phenomenon (drawdown) in which the parison hangs down due to its own weight tends to occur. In order to reduce this drawdown, it is necessary to use a resin having a sufficiently high melt viscosity and melt tension. A method of increasing the molecular weight is adopted in order to improve the drawdown resistance of polyethylene, but there is a problem that the melt viscosity becomes high and the extrusion characteristics (extrusion amount, parison surface state) deteriorate. As a method for solving this problem, a multi-stage polymerization method (Patent Document 1), a method of mixing two-component polyethylene in a specific ratio (Patent Document 2), a fluoropolymer, hydrotalcite, etc. in a polyethylene resin are used. A method of adding (Patent Document 3) and the like are known. However, the polyethylene improved by the above method contains a large amount of metal and is not suitable for a container for high-purity chemicals.

Japanese Unexamined Patent Publication No. 55-152735 Japanese Unexamined Patent Publication No. 6-29909 Japanese Unexamined Patent Publication No. 2009-138122

The present invention is to provide a polyethylene-based resin composition suitable for a container for high-purity chemicals, which reduces deterioration of the molded surface of the container obtained by blow molding and suppresses elution of fine particles and metals.

As a result of diligent studies to solve the above problems, the present inventors reduced the molding surface of the container in blow molding by adding vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene copolymer to high-density polyethylene. However, it has been found that the elution of fine particles and metals can be suppressed, and the present invention has been completed.

That is, each aspect of the present invention is [1] to [7] shown below.
[1] Polyethylene resin 99.90 to 99.99% by weight satisfying the following requirements (1) to (5), and 0.01 to 0.10 weight by weight of vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer. % Is a polyethylene resin composition.
(1) Density (JIS K6922-1) is 940-970 kg / m ³
(2) Melt flow rate (JIS K6922-1) at 190 ° C. and 21.6 kg load is 2.0 to 12 g / 10 minutes (3) Weight average molecular weight (Mw) determined by gel permeation chromatography (GPC). And the ratio (Mw / Mn) of the number average molecular weight (Mn) is 8.0 to 15.
(4) In the molecular weight distribution curve obtained by gel permeation chromatography (GPC), 0.50% by weight or less of the components having a molecular weight of 1000 or less (5) 20 ppm or less of the contained metal content [2] [1]. A container for high-purity chemicals, which is characterized by being made of a polyethylene-based resin composition of.
[3] The container for high-purity chemicals according to [2], wherein the number of fine particles of 0.1 μm or more eluted from the container is 25 / mL or less.
[4] The container for high-purity chemicals according to [2] or [3], wherein the content of metal is 20 ppm or less.
[5] The container for high-purity chemicals according to any one of [2] to [4], wherein the maximum roughness of the inner surface of the container is 10 μm or less.

The polyethylene-based resin composition according to one aspect of the present invention can reduce the pressure load during molding, thereby lowering the processing temperature and reducing the decomposition of polyethylene during molding. The container made of the polyethylene-based resin composition has better skin and cleanliness of the molded product than the conventional polyethylene container, and is used in parts cleaning, etching processes, etc. in the semiconductor field, precision industrial parts field, etc. It can be provided as a container for high-purity chemicals required.

The polyethylene-based resin composition according to one aspect of the present invention contains a polyethylene resin satisfying the above requirements (1) to (5) and a vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer, and when molded. The container has excellent molded skin and suppresses the elution of fine particles and metals, and is particularly suitable for containers of high-purity chemicals, which have a problem of contamination with foreign substances such as fine particles.

As the polyethylene resin constituting the polyethylene-based resin composition, any polyethylene-based resin satisfying the above requirements (1) to (5) can be used without any limitation.

Here, when the polyethylene resin is an ethylene-α-olefin copolymer, the α-olefin at that time may be, for example, propylene, 1-butene, 4-methyl-1-pentene, 1-pentene, 1-hexene. , 1-octene, 1-nonene, 1-decene, 1-hexadecene, 1-octadecene and the like, and a Cheegler-based catalyst is suitable as the highly active polymerization catalyst at that time. As a specific example, examples of the Ziegler-based catalyst include a catalyst composed of a solid catalyst component that requires titanium, magnesium, and halogen, and an organoaluminum compound. By producing polyethylene using a Ziegler-based polymerization catalyst, it becomes possible to obtain a polyethylene-based resin composition containing a small amount of metal. Further, the polyethylene resin does not contain additives.

For example, the polyethylene resin can be produced by the following two-stage polymerization method.

Ziegler-based catalyst containing Al, Ti, Mg and Cl as main components, solvent (hexane), ethylene (concentration 8-12 g / kg-solvent), hydrogen (concentration 0.15-) prepared in accordance with JP-A-7-41513. 0.30 g / kg-solvent) and triisobutylaluminum (concentration 0.10 to 0.20 g / kg-solvent) were continuously supplied to the first-stage polymerizer, and the temperature was 80 to 85 ° C., the total pressure was 3,000 kPa, and the average. Ethylene polymerization (low molecular weight component) is performed under the condition of residence time of 2 hours. The hexane slurry containing the first-stage polymer is continuously supplied to another second-stage polymer after removing unreacted hydrogen and ethylene in a flash tank. In the second stage polymerizer, ethylene (concentration 10 to 15 g / kg-solvent), hydrogen (concentration 0.008 to 0.02 g / kg-solvent), 1-butene (concentration 1.0 to 2.5 g / kg). -Solvent) is supplied, and ethylene polymerization (high molecular weight component) is performed under the conditions of a temperature of 75 to 85 ° C., a total pressure of 2,000 kPa, and an average residence time of 2 hours. The hexane slurry of the second-stage polymer is sent to a flash tank to remove unreacted hydrogen, ethylene, and 1-butene, and then the drying step is removed to obtain a mixture powder of an ethylene-based copolymer. The proportion of the low molecular weight component is 47 to 49% by weight, and the proportion of the high molecular weight component is 51 to 53% by weight. A polyethylene resin can be obtained by pelletizing the two-stage polymerized powder in the above production process without adding additives.

The vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer constituting the polyethylene resin composition is one of the fluorinated olefin copolymers typified by vinylidene fluoride, vinyl fluoride, tetrafluoroethylene and hexafluoropropylene. It is a seed, and among these, it is a polyethylene-based resin composition for containers used for high-purity chemicals, which has an excellent molded surface and suppresses the generation of foreign substances such as fine particles and metals. A fluorine-based polymer component containing an inorganic anti-adhesive agent is commercially available. However, if an anti-adhesive agent is added, the metal content increases and the number of fine particles eluted from the container increases, resulting in adhesiveness. It is preferable that the inhibitor is not blended. As the vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer, for example (trade name) Dynamer FX5911 (manufactured by 3M Japan Ltd.) can be obtained as a commercially available product. Moreover, it is preferable that the polyethylene-based resin composition of the present invention does not contain other components.

The blending ratio of the vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer to be blended with the polyethylene resin is 0.01 to 0.1% by weight, preferably 0.01 to 0.05% by weight with respect to the polyethylene resin. %. If the addition amount is less than 0.01% by weight, the molded product obtained by blow molding the obtained polyethylene-based resin composition will have rough skin. On the other hand, if it exceeds 0.1% by weight, not only does it not have a great effect on the molded product, but also the amount of vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer to be added increases, which adversely affects cleanliness and the like.

The density of the polyethylene resin (JIS K6922-1) is 940 to 960 kg / m ³ . If the range density of 940~960kg / ^{m 3,} is less than 940 kg / ^{m 3} and increased amount of low molecular weight components that cause particulates, clean of the container is reduced. Further, when the density ^{exceeds 960 kg / m 3} , the strength of the container is further lowered.

The melt flow rate of the polyethylene resin at 190 ° C. and a load of 21.6 kg (JIS K6922-1, hereinafter referred to as HLMFR) is 2.0 to 12 g / 10 minutes, preferably 5.0 to 10 g / 10 minutes. Is. When the HLMFR is less than 2.0 g / 10 minutes, the melt viscosity becomes too high, so that not only the extrusion load during the molding process becomes high, but also the rough skin of the molded product is induced. On the other hand, when it exceeds 12 g / min, the melt tension becomes small, and when molding a large container of 200 L or more, the drawdown during the molding process is severe and the molding processability is inferior.

The ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) obtained by gel permeation chromatography (GPC) of the polyethylene resin is 8.0 to 15. When Mw / Mn is less than 8.0, the melt viscosity becomes too high, so that not only the extrusion load during the molding process becomes high, but also the rough skin of the molded product is induced. On the other hand, when Mw / Mn exceeds 15, the molecular weight distribution is expanded, the low molecular weight component is increased, and the number of fine particles eluted from the container is increased. In addition, the shape of the pinch-off portion, which is the parison joint portion, deteriorates, and the drop strength of the container decreases.

In the molecular weight distribution curve obtained by using gel permeation chromatography (GPC) of a polyethylene resin, the component having a molecular weight of 1000 or less is 0.50% by weight or less. When the component having a molecular weight of 1000 or less exceeds 0.50% by weight, the low molecular weight component increases and the number of fine particles eluted from the container increases.

The amount of metal contained in the polyethylene resin is 20 ppm or less, preferably 15 ppm or less. When the amount of metal contained is 20 ppm or less, the amount of metal eluted into high-purity chemicals is small, so that the concentration of metal impurities in the chemicals can be suppressed. The amount of metal contained is the ratio of the metal content to the total resin in ppm by weight. The amount of metal contained is obtained by alkali melting after ashing the resin, and is a residue of Mg, Al, Ti and the like.

The high-purity chemical container according to one aspect of the present invention is made of the above-mentioned polyethylene-based resin composition. A high-purity chemical container is obtained by molding the polyethylene-based resin composition into a container shape by blow molding. In particular, a blow molding method using a blow molding machine installed in a clean room and using compressed air from which impurities have been removed by a filter as blow air is preferable for producing a clean container.

The number of fine particles of 0.1 μm or more eluted from the high-purity chemical container is preferably 25 / mL or less, and more preferably 20 / mL or less. When the number of fine particles of 0.1 μm or more is 25 / mL or less, the amount of fine particles eluted into the high-purity chemical is small, so that the concentration of impurities in the chemical can be suppressed. The number of fine particles is measured by filling a high-purity chemical container with ultrapure water and measuring the number of fine particles of 0.1 μm or more in the filled water with a fine particle counter.

The maximum roughness of the inner surface of the container for high-purity chemicals (hereinafter referred to as Rz) is preferably 10 μm or less. When Rz exceeds 10 μm, the appearance of the molded product is inferior. Furthermore, air bubbles in the chemicals stay in the rough skin and are detected as fine particles, which causes an increase in the number of fine particles. Rz is the sum of the height of the highest mountain and the depth of the deepest valley in the roughness curve at the reference length.

The amount of metal contained in the high-purity chemical container is preferably 20 ppm. When the amount of metal contained is 20 ppm or less, the concentration of metal impurities in the chemical can be suppressed.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples. The polyethylene resin, fluoropolymer, blow molding machine and test method used in Examples and Comparative Examples are as follows.

(1) Polyethylene resin Polyethylene A: Density = 946 kg / m ³ , HLMFR = 6.3 g / 10 minutes, Mw / Mn = 14, component with molecular weight of 1000 or less = 0.40% by weight, metal content = 14 ppm
Polyethylene B: Density = 957 kg / m ³ , HLMFR = 8.0 g / 10 minutes, Mw / Mn = 13, component with molecular weight 1000 or less = 0.26% by weight, metal content = 13 ppm
(Product name: Niporon Hard 8D01A, manufactured by Tosoh Corporation)
Polyethylene C: Density = 954 kg / m ³ , HLMFR = 35 g / 10 minutes, Mw / Mn = 12, component with molecular weight 1000 or less = 1.08% by weight, metal content = 85 ppm
(Product name: Niporon Hard 8300A, manufactured by Tosoh Corporation)
Polyethylene D: Density = 950 kg / m ³ , HLMFR = 9.4 g / 10 minutes, Mw / Mn = 13, component with molecular weight 1000 or less = 0.53% by weight, metal content = 17 ppm

Polyethylene A and polyethylene D were produced by the following two-stage polymerization method.

[Manufacturing of polyethylene A]
Ziegler-based catalyst containing Mg, Al, Ti and Cl as main components, solvent (hexane), ethylene (concentration 8-10 g / kg-solvent), hydrogen (concentration 0.15-) prepared in accordance with JP-A-7-41513. 0.25 g / kg-solvent) and triisobutylaluminum (concentration 0.10 to 0.20 g / kg-solvent) were continuously supplied to the first-stage polymerizer at a temperature of 80 to 85 ° C. and a total pressure of 3,000 kPa. Ethylene polymerization (low molecular weight component) was carried out under the condition of an average residence time of 2 hours. The hexane slurry containing the first-stage polymer was continuously supplied to another second-stage polymer after removing unreacted hydrogen and ethylene in a flash tank. In the second stage polymerizer, ethylene (concentration 10 to 15 g / kg-solvent), hydrogen (0.008 to 0.010 g / kg-solvent), 1-butene (2.0 to 2.5 g / kg-solvent). ), And ethylene polymerization (high molecular weight component) was carried out under the conditions of a temperature of 75 to 85 ° C., a total pressure of 2,000 kPa, and an average residence time of 2 hours. The hexane slurry of the second-stage polymer was sent to a flash tank to remove unreacted hydrogen, ethylene, and 1-butene, and then a drying step was performed to obtain a mixture powder of an ethylene-based copolymer. 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 two-stage polymerized powder in the above production process was pelletized without additives to obtain polyethylene A.

[Manufacturing of polyethylene D]
Ziegler-based catalyst containing Mg, Al, Ti and Cl as main components, solvent (hexane), ethylene (concentration 9-11 g / kg-solvent), hydrogen (concentration 0.30 to 0.30) prepared in accordance with JP-A-7-41513. 0.50 g / kg-solvent) and triisobutylaluminum (concentration 0.10 to 0.20 g / kg-solvent) were continuously supplied to the first-stage polymerizer at a temperature of 80 to 85 ° C. and a total pressure of 3,000 kPa. Ethylene polymerization (low molecular weight component) was carried out under the condition of an average residence time of 2 hours. The hexane slurry containing the first-stage polymer was continuously supplied to another second-stage polymer after removing unreacted hydrogen and ethylene in a flash tank. In the second stage polymerizer, ethylene (concentration 10 to 13 g / kg-solvent), hydrogen (0.010 to 0.015 g / kg-solvent), 1-butene (8.5-10 g / kg-solvent) were further added. It was supplied and subjected to ethylene polymerization (high molecular weight component) under the conditions of a temperature of 75 to 85 ° C., a total pressure of 2,000 kPa, and an average residence time of 2 hours. The hexane slurry of the second-stage polymer was sent to a flash tank to remove unreacted hydrogen, ethylene, and 1-butene, and then a drying step was performed to obtain a mixture powder of 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 two-stage polymerized powder in the above production process was pelletized without additives to obtain polyethylene D.

(2) Fluorine-based polymer Fluorine-based polymer A: Vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (trade name: Dynamar FX5911, manufactured by 3M Japan Co., Ltd.)
Fluorine-based polymer B: Vinylidene fluoride / hexafluoropropylene copolymer (trade name: Dynamar FX9613, manufactured by 3M Japan Ltd.)

(3) Blow molding machine Electric blow molding machine, MSE-50E / 54M-A (manufactured by Tahara Co., Ltd.)

(4) Blow molding of 800 mL container Using a blow molding machine (manufactured by Tahara Co., Ltd.) having a 50 mmΦ extrusion screw, the parison is continuously extruded from the tip of the die at a cylinder temperature of 190 to 200 ° C. and a screw rotation speed of 16 to 18 rotations. A container having an average wall thickness of 1 mm and an internal volume of 800 mL was molded.

(5) Number of fine particles An internal volume 800 mL container obtained by blow molding a polyethylene-based resin composition was used. Fill the container with 600 mL of ultrapure water in a clean room, cover it, store it in a clean oven with a set temperature of 40 ° C (DE411 manufactured by Yamato Kagaku Co., Ltd.) for 35 days, and then store it at 0.1 μm or more in the filled water. The number of fine particles was measured with a fine particle counter (manufactured by Rion Co., Ltd., controller: KE-40B1, particle sensor: KS-42A). The number of fine particles in water is shown in pieces / mL.

(6) Surface Roughness A container having an internal volume of 800 mL obtained by blow molding a polyethylene-based resin composition was used.

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).

(7) Amount of metal contained The sample was incinerated and then alkaline-melted, and the solution was used as a measurement solution, and the amount of metal contained in the sample was measured by ICP-AES measurement.

Example 1
A 99.99% by weight polyethylene A and 0.01% by weight a fluoropolymer A were melt-kneaded and then cut to obtain a composition. Using the obtained composition, a container having an internal volume of 800 mL was prepared by blow molding. The resin pressure at the time of molding was 2.7 MPa lower than that in the case of molding only with polyethylene A. The number of fine particles eluted from the obtained container, Rz on the inner surface of the container, and the amount of metal contained in the container were measured. The results are shown in Table 2. The number of fine particles of 0.1 μm or more was 20 / mL, the Rz was 9.9 μm, and the amount of metal contained was 14 ppm.

Example 2
Polyethylene A 99.97% by weight and fluorinated polymer A 0.03% by weight were melt-kneaded and then cut to obtain a composition. Using the obtained composition, a container having an internal volume of 800 mL was prepared by blow molding. The resin pressure at the time of molding was 3.6 MPa lower than that in the case of molding only with polyethylene A. The number of fine particles eluted from the obtained container, Rz on the inner surface of the container, and the amount of metal contained in the container were measured. The results are shown in Table 3. The number of fine particles of 0.1 μm or more was 17 / mL, the Rz was 8.7 μm, and the amount of metal contained was 14 ppm.

Example 3
Polyethylene A 99.95% by weight and fluorinated polymer A 0.05% by weight were melt-kneaded and then cut to obtain a composition. Using the obtained composition, a container having an internal volume of 800 mL was prepared by blow molding. The resin pressure at the time of molding was 3.6 MPa lower than that in the case of molding only with polyethylene A. The number of fine particles eluted from the obtained container, Rz on the inner surface of the container, and the amount of metal contained in the container were measured. The results are shown in Table 3. The number of fine particles of 0.1 μm or more was 22 / mL, the Rz was 8.5 μm, and the amount of metal contained was 14 ppm.

Example 4
Polyethylene B 99.95% by weight and fluoropolymer A 0.05% by weight were melt-kneaded and then cut to obtain a composition. Using the obtained composition, a container having an internal volume of 800 mL was prepared by blow molding. The resin pressure at the time of molding was 3.1 MPa lower than that in the case of molding only with polyethylene B. The number of fine particles eluted from the obtained container, Rz on the inner surface of the container, and the amount of metal contained in the container were measured. The results are shown in Table 3. The number of fine particles of 0.1 μm or more was 19 / mL, the Rz was 7.8 μm, and the contained metal was 13 ppm.

Comparative Example 1
99.99% by weight of polyethylene A and 0.01% by weight of the fluoropolymer B were melt-kneaded and then cut to obtain a composition. Using the obtained composition, a container having an internal volume of 800 mL was prepared by blow molding. The resin pressure at the time of molding was 1.3 MPa lower than that in the case of molding only with polyethylene A. The number of fine particles eluted from the obtained container, Rz on the inner surface of the container, and the amount of metal contained in the container were measured. The results are shown in Table 3. The number of fine particles of 0.1 μm or more was 40 / mL, the Rz was 10.1 μm, and the amount of metal contained was 22 ppm.

Comparative Example 2
Polyethylene A 99.97% by weight and fluorinated polymer B 0.03% by weight were melt-kneaded and then cut to obtain a composition. Using the obtained composition, a container having an internal volume of 800 mL was prepared by blow molding. The resin pressure at the time of molding was 1.9 MPa lower than that in the case of molding only with polyethylene A. The number of fine particles eluted from the obtained container, Rz on the inner surface of the container, and the amount of metal contained in the container were measured. The results are shown in Table 3. The number of fine particles of 0.1 μm or more was 58 / mL, the Rz was 9.1 μm, and the amount of metal contained was 35 ppm.

Comparative Example 3
Polyethylene A 99.95% by weight and fluorinated polymer B 0.05% by weight were melt-kneaded and then cut to obtain a composition. Using the obtained composition, a container having an internal volume of 800 mL was prepared by blow molding. The resin pressure at the time of molding was 2.3 MPa lower than that in the case of molding only with polyethylene A. The number of fine particles eluted from the obtained container, Rz on the inner surface of the container, and the amount of metal contained in the container were measured. The results are shown in Table 3. The number of fine particles of 0.1 μm or more was 76 / mL, the Rz was 8.1 μm, and the amount of metal contained was 45 ppm.

Comparative Example 4
Polyethylene B 99.99% by weight and fluoropolymer B 0.01% by weight were melt-kneaded and then cut to obtain a composition. Using the obtained composition, a container having an internal volume of 800 mL was prepared by blow molding. The resin pressure at the time of molding was 2.1 MPa lower than that in the case of molding only with polyethylene B. The number of fine particles eluted from the obtained container, Rz on the inner surface of the container, and the amount of metal contained in the container were measured. The results are shown in Table 3. The number of fine particles of 0.1 μm or more was 38 / mL, the Rz was 8.0 μm, and the amount of metal contained was 22 ppm.

Comparative Example 5
Polyethylene C 99.99% by weight and fluoropolymer A 0.01% by weight were melt-kneaded and then cut to obtain a composition. Using the obtained composition, a container having an internal volume of 800 mL was prepared by blow molding. The resin pressure at the time of molding was 1.6 MPa lower than that in the case of molding only with polyethylene C. The number of fine particles eluted from the obtained container, Rz on the inner surface of the container, and the amount of metal contained in the container were measured. The results are shown in Table 3. The number of fine particles of 0.1 μm or more was 280 / mL, the Rz was 7.9 μm, and the amount of metal contained was 85 ppm.

Comparative Example 6
Polyethylene D99.99% by weight and fluoropolymer A 0.01% by weight were melt-kneaded and then cut to obtain a composition. Using the obtained composition, a container having an internal volume of 800 mL was prepared by blow molding. The resin temperature at the time of molding was 1.8 MPa lower than that in the case of molding only with polyethylene D. The number of fine particles eluted from the obtained container, Rz on the inner surface of the container, and the amount of metal contained in the container were measured. The results are shown in Table 3. The number of fine particles of 0.1 μm or more was 28 / mL, the Rz was 8.1 μm, and the amount of metal contained was 17 ppm.

Claims (5)

Contains 99.90 to 99.99% by weight of polyethylene resin satisfying the following requirements (1) to (5), and 0.01 to 0.10% by weight of vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer. Polyethylene resin composition.
(1) Density (JIS K6922-1) is 940-960 kg / m ³
(2) Melt flow rate (JIS K6922-1) at 190 ° C. and 21.6 kg load is 2.0 to 12 g / 10 minutes (3) Weight average molecular weight (Mw) determined by gel permeation chromatography (GPC). And the ratio (Mw / Mn) of the number average molecular weight (Mn) is 8.0 to 15.
(4) In the molecular weight distribution curve obtained by gel permeation chromatography (GPC), 0.50% by weight or less of the components having a molecular weight of 1000 or less (5) 20 ppm or less of the contained metal content. A container for high-purity chemicals, which comprises the polyethylene-based resin composition according to claim 1. The container for high-purity chemicals according to claim 2, wherein the number of fine particles of 0.1 μm or more eluted from the container is 25 / mL or less. The container for high-purity chemicals according to claim 2 or 3, wherein the content of metal is 20 ppm or less. The container for high-purity chemicals according to any one of claims 2 to 4, wherein the maximum roughness of the inner surface of the container is 10 μm or less.