JP7243223B2 - Method for manufacturing high-purity chemical container - Google Patents

Description

INDUSTRIAL APPLICABILITY The present invention is suitable for the manufacture of high-purity chemical containers used in the fields of the semiconductor device industry, precision industrial parts, and pharmaceuticals. The present invention relates to a method for manufacturing a high-purity chemical container which is extremely small and excellent in cleanness.

In recent years, the demand for high-purity chemicals has increased along with the remarkable development of the electronics industry. High-purity chemicals are used, for example, as essential chemicals for the manufacture of electronic circuits such as large-scale integrated LSIs. Specifically, for wafer cleaning/etching, wiring/insulating film etching, jig cleaning, developer, resist diluent, resist remover, drying, etc., sulfuric acid, hydrochloric acid, nitric acid, hydrogen fluoride Acid, ammonium fluoride, hydrogen peroxide solution, isopropyl alcohol, xylene, TMAH, methanol, acetic acid, phosphoric acid, aqueous ammonia, PGMEA, DMSO, NMP, ECA, ethyl lactate, etc. are used. Conventionally, polyethylene resins have been used as container materials for these high-purity chemicals in terms of chemical resistance, impact resistance, price, and the like. However, conventional containers made of polyethylene resin have the problem of contamination of the contents with contaminants such as eluted substances and degraded substances of the resin caused by chemicals, and there is a limit as a container for high-purity chemicals. That is, with the miniaturization of VLSI, the metal impurity concentration, which was conventionally 1PPB, is now required to be 1PPT or less. In addition, although fine particles of 0.5 μm or more have been a problem in the past, a strict quality requirement of 100 or less particles/ml of 0.2 μm or more has come to be demanded. Fine particles have become a problem, and stricter quality requirements are being demanded, with fine particles of 0.1 μm or more being 100/ml or less. Therefore, the appearance of a high-purity chemical container that satisfies the metal impurity concentration and fine particle level and is excellent in cleanliness is awaited.

Here, there is a proposal for a container made of polyethylene resin and molded at a temperature of 173 to 190 ° C. with very little elution of impure fine particles. , see Patent Document 1).

Also, there is a proposal for a clean hollow container molding method using clean air, but there is no description regarding the evaluation of fine particles eluted from the container (see, for example, Patent Document 2).

JP-A-7-257540 JP-A-8-192455

The present invention relates to a method for producing a polyethylene resin container by blow molding, in which the container is molded using a screw having a specific shape with a blow molding machine, and when used as a high-purity chemical container, the resin is exposed to chemicals. To provide a method for producing a high-purity chemical container that can be used for a long period of time while minimizing the elution of contaminants such as eluted substances and degraded substances from resin, and less discoloration of the resin.

As a result of intensive studies on the screw shape of a blow molding machine in producing a container made of polyethylene resin having specific properties, the present inventor found that a container with excellent cleanliness can be obtained, and arrived at the present invention. .

That is, each aspect of the present invention is [1] to [5] shown below.
[1] In the method of manufacturing a container by blow molding polyethylene resin, the screw shape of the blow molding machine satisfies the following conditions (1) to (3), and the molten resin (parison) extruded by the screw A method for producing a high-purity chemical container, characterized in that the temperature is in the range of 170°C to 210°C.
(1) The ratio of the screw effective length L to the screw diameter D (L/D ratio) is in the range of 24 to 32. (2) The groove depth of the screw in the feed section is in the range of 0.1D to 0.3D. Range (3) Range where the ratio of the groove depth of the supply portion to the groove depth of the compression portion is 0.80 to 1.00 [2] 0.1 μm eluted from the high-purity chemical container obtained by blow molding The method for producing a high-purity chemical container according to [1] above, wherein the number of fine particles is 10/mL or less.
[3] The polyethylene resin contains two components: a low molecular weight component with a density of 940 to 980 kg/m ³ and a high molecular weight component with a density of 920 to 950 kg/m ³ and a density lower than the low molecular weight component, and The weight ratio of the low molecular weight component: high molecular weight component = 20:80 to 80:20, and the following [1] or [2] using the one having the properties of (1) to (5) A method for manufacturing a high-purity chemical container.
(1) Density (JIS K6922-1: 1997) is 940 to 970 kg/m ³
(2) Melt flow rate (JIS K6922-1: 1997) at 190° C. and 21.6 kg load is 2.0 to 15 g/10 minutes (3) Weight average molecular weight determined by gel permeation chromatography (GPC) ( Mw) to number average molecular weight (Mn) ratio (Mw / Mn) is 8 to 15
(4) In the molecular weight distribution curve obtained using gel permeation chromatography (GPC), the content of components having a molecular weight of 1000 or less is 0.50% by weight or less (5) The amount of chlorine contained is 8 PPM or less relative to the polyethylene resin [4 ] The method for producing a high-purity chemical container according to any one of the above [1] to [3], wherein the polyethylene resin contains ash in an amount of 30 PPM or less relative to the resin.
[5] The method for producing a high-purity chemical container according to any one of [1] to [4] above, wherein the polyethylene resin does not contain additives.

The ratio of the screw effective length L to the screw diameter D (L/D ratio) of the present invention is 24-32, more preferably 25-28. If L/D is 24 or more, the polyethylene resin can be sufficiently melt-kneaded. Also, if L/D is 32 or less, the capacity of the motor for driving the screw becomes a load that does not pose an economic problem.

The groove depth of the screw in the feeding section of the present invention is 0.1D to 0.3D, more preferably 0.1D to 0.15D. If the groove depth of the feed section is less than 0.1D, the amount of extrusion is too small, so in direct blow molding, etc., the parison descending time is long until the parison reaches the desired length that matches the mold shape. This results in a longer molding cycle. On the other hand, if the groove depth of the feeding section is larger than 0.3D, the output will increase, so the motor load will increase, and a screw extruder motor with a larger motor capacity will be required or the screw will break. there's a possibility that.

Also, the ratio of the groove depth of the supply portion to the groove depth of the compression portion of the present invention is 0.80 to 1.00, more preferably 0.80 to 0.90. If the groove depth ratio is less than 0.80, the motor load increases due to an increase in extrusion rate, and the screw may be damaged. If the ratio of the groove depths is greater than 1.00, insufficient heating of the resin in the supply section and the compression section causes poor plasticization, resulting in a reduced extrusion rate. The parison descending time to reach the length of the parison becomes longer, resulting in a longer molding cycle.

The screw shape of the present invention preferably has a ratio of the length of the feeding portion to the effective length of the screw of 0.35 to 0.50. Sufficient preheating of the polyethylene can be provided when the length ratio of the feed section is in the range of 0.35 to 0.50.

The screw shape of the present invention preferably has a ratio of the length of the compressed portion to the effective length of the screw of 0.30 to 0.40. When the length ratio of the compressed portion is 0.30 to 0.40, the polyethylene can be sufficiently melt-kneaded.

The screw shape of the present invention preferably has a ratio of the length of the metering portion to the effective length of the screw of 0.20 to 0.30. When the ratio of the lengths of the metering portions is in the range of 0.20 to 0.30, the polyethylene can be extruded with little variation in extrusion rate (surging phenomenon).

Further, in the screw shape, there is a case where the metering portion is provided with unevenness different from the screw shape such as Murdoch in order to increase the shearing effect.

The molten resin (parison) temperature extruded by the screw of the present invention ranges from 170°C to 210°C. When the molten resin (parison) temperature is lower than 170°C, the polyethylene resin cannot be sufficiently melt-kneaded. If the molten resin (parison) temperature is higher than 210° C., the molten resin deteriorates, affecting the cleanliness of the molded container. The molten resin (parison) temperature can be controlled by the temperature of the cylinder in the screw, and can be controlled within the above range by setting it in the range of 160°C to 200°C.

It is preferable that the number of fine particles of 0.1 μm or more eluted from the high-purity chemical container manufactured according to the present invention is 10/mL or less. If the number of fine particles of 0.1 μm or more is 10/mL or less, it is possible to cope with miniaturization of LSI.

The polyethylene resin used in the present invention comprises a low molecular weight component with a density of 0.94 to 0.98 g/cm ³ and a high molecular weight component with a density of 0.92 to 0.95 g/cm ³ and a lower density than the low molecular weight component. The weight ratio of the two components is low molecular weight component: high molecular weight component = 20:80 to 80:20, and the following properties (1) to (5) are used. is preferred.
(1) Density (JIS K6922-1) is 0.94 to 0.97 g/cm ³
(2) Melt flow rate (JIS K6922-1: 1997) at 190° C. and 21.6 kg load is 2.0 to 15 g/10 minutes (3) Weight average molecular weight determined by gel permeation chromatography (GPC) ( Mw) to number average molecular weight (Mn) ratio (Mw / Mn) is 8 to 15
(4) In the molecular weight distribution curve obtained using gel permeation chromatography (GPC), the content of components having a molecular weight of 1000 or less is 0.50% by weight or less (5) The amount of chlorine contained is 8 PPM or less relative to the polyethylene resin Further, A polyethylene resin having an ash content of 30 PPM or less relative to the resin is preferred. Moreover, it is preferable that the polyethylene resin does not contain additives.

The polyethylene resin used in the present invention can be produced using a highly active catalyst such as a Ziegler catalyst or a metallocene catalyst. For example, using a highly active Ziegler catalyst composed of a transition metal compound such as titanium and zirconium, a magnesium compound, and an organoaluminum compound as a polymerization catalyst, ethylene or ethylene and an α-olefin having 3 to 20 carbon atoms is mixed to a desired density. It is produced by copolymerizing in a ratio of

The catalyst in that case can include the catalyst described in Japanese Patent No. 3,319,051.

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, 1-eicosene and the like. be able to.

The polymerization method in the production of the polyethylene resin is to keep the concentration of metal impurities eluted in chemicals low and to limit the incorporation of low-molecular-weight polymers that cause the generation of fine particles into the resin. 10 or less polymerization medium, for example, normal hexane, normal heptane, etc., a low molecular weight component with a density of 0.94 to 0.98 g/cm ³ and a low molecular weight component with a density of 0.92 to 0.95 g/cm ³ contains two components, a high molecular weight component having a lower density than the low molecular weight component, and the weight ratio of the two components is low molecular weight component:high molecular weight component=20:80 to 80:20. Two components, a low molecular weight component and a high molecular weight component, are produced, for example, by a two-stage polymerization method.

In addition, the polyethylene resin is specified in terms of density, melt flow rate, molecular weight distribution (Mw/Mn), melting temperature, components with a molecular weight of 1000 or less, xylene extractables at 25°C, and chlorine content, as shown below. .

That is, the density of the polyethylene resin (JIS K6922-1:1997) is 940-970 kg/m ³ , preferably 950-960 kg/m ³ . If the density is in the range of 940 to 970 kg/m ³ , the container can be formed without any problem of cleanliness and strength due to generation of fine particles.

The melt flow rate (JIS K6922-1:1997) of the polyethylene resin at 190° C. and 21.6 kg load is 2.0 to 15 g/10 minutes, preferably 5.0 to 10 g/10 minutes. If the melt flow rate is in the range of 2.0 to 15 g/10 minutes, deterioration of the surface texture of the container can be suppressed.

The ratio Mw/Mn of the weight average molecular weight (Mw) to the number average molecular weight (Mn) determined by gel permeation chromatography (GPC) of the polyethylene resin is 8-15. When the Mw/Mn is in the range of 8 to 15, deterioration of the surface texture of the container can be suppressed, and the container can be molded without problems in cleanliness and drop strength due to generation of fine particles.

In a molecular weight distribution curve obtained using gel permeation chromatography (GPC), it is preferable that the content of components having a molecular weight of 1000 or less is 0.50% by weight or less. More preferably, it is 0.30% by weight or less. If the content of the component having a molecular weight of 1000 or less is 0.50% by weight or less, the container can be molded without any problem of cleanliness due to generation of fine particles.

The chlorine content of the polyethylene resin measured with a fluorescent X-ray device is preferably 8 PPM or less with respect to the entire polyethylene resin. If the amount of chlorine contained is 8 PPM or less with respect to all polyethylene resins, discoloration of the container can be suppressed. If it exceeds 8 PPM for all polyethylene resins, chlorine causes discoloration of the container, resulting in poor appearance. In addition, since it corrodes the metals of the molding machine and the mold, a neutralizing agent for supplementing chlorine is required, and the neutralizing agent used unavoidably causes metal impurities.

Also, the ash content contained in the polyethylene resin is preferably 30 PPM or less relative to the resin. If the amount of ash contained in the polyethylene resin is 30 PPM or less, the amount of ash eluted into the chemical is small, so the concentration of metal impurities in the chemical can be suppressed. Ash content indicates the percentage of completely ash to total resin in parts per million by weight. Completely incinerated products are obtained by complete incineration in an electric furnace, and include residuals of polymerization catalysts such as Al, Mg, Ti, and Si, metal-containing additives such as neutralizers, and impurities and impurities during polyethylene resin production. Deposits are metal oxides.

The polyethylene resin can be molded into a container shape by blow molding to form a high-purity chemical 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 by a filter is preferable for manufacturing clean containers.

Depending on the type of chemical, it is necessary to make it a light-shielding container, and a multilayer container containing at least one layer containing a light-shielding material such as an organic pigment or an inorganic pigment with the polyethylene resin as an inner layer is also possible. An organic pigment or an inorganic pigment may be added to the polyethylene resin inside.

When a container is molded using a screw having the shape of the present invention, a clean container that can handle miniaturization of ultra-LSI by suppressing contaminants such as elution and deterioration of the polyethylene resin due to chemicals and metal impurities as much as possible. can provide

EXAMPLES The present invention will now be described with reference to examples and comparative examples. The polyethylene resin, blow molding machine, screw shape, and test method used in Examples and Comparative Examples are as follows.

(1) Polyethylene resin Density = 957 g/cm ³ , MFR = 8.0 g/10 minutes (load: 21.6 kgf, temperature: 190°C), Mw/Mn = 13, components with a molecular weight of 1000 or less = 0.26% by weight , chlorine content = 2 PPM, ash content = 16 PPM

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

(3) Screw Shape Screws used in Examples and Comparative Examples have shapes described in Table 1.

(4) Number of fine particles: A container with an inner volume of 800 mL obtained by blow molding the polyethylene was used. Fill the container with 800 ml of ultrapure water in a clean room, cover it and leave it for 1 hour. 42A). The number of microparticles in water is given in particles/ml.

(5) Extrusion characteristics Using an electric blow molding machine (manufactured by Tahara Co., Ltd.) in which a screw of shape A is inserted, the polyethylene is extruded at a cylinder setting temperature of 180 ° C. to 220 ° C. and a rotation speed of 10 to 40 rpm, The extrusion rate (kg/h) of the polyethylene with respect to the screw rotation speed was measured. The results are listed in Table 2.
In addition, using an electric blow molding machine (manufactured by Tahara Co., Ltd.) in which a screw of shape B is inserted, the polyethylene is extruded at a cylinder setting temperature of 180 ° C. to 220 ° C. and a rotation speed of 10 to 60 rpm, and a screw rotation speed. The extrusion rate (kg/h) of the polyethylene was measured. The results are listed in Table 3.

Example 1
Using an electric blow molding machine (manufactured by Tahara Co., Ltd.) in which a screw of shape A is inserted, the polyethylene is extruded at a cylinder setting temperature of 180 ° C., a screw rotation speed of 26.0 rpm, and an extrusion rate of 20 kg / h, and the molding cycle is 27. A container with an internal volume of 800 mL and a weight of 120 g was molded in seconds. The parison temperature was 184.6°C. The fine particle measurement described above was performed using the obtained container. As shown in Table 4, the number of fine particles of 0.1 µm or more was 6.2/mL.

Example 2
Using the same molding machine as in Example 1, the polyethylene was extruded at a cylinder setting temperature of 200 ° C., a screw rotation speed of 25.5 rpm, and an extrusion rate of 20 kg / h, and a molding cycle of 27 seconds and an inner volume of 800 mL container with a weight of 120 g. was molded. The parison temperature was 204.8°C. The fine particle measurement described above was performed using the obtained container. As shown in Table 4, the number of fine particles of 0.1 µm or more was 8.5/mL.

Comparative example 1
Using the same molding machine as in Example 1, the polyethylene was extruded at a cylinder setting temperature of 220 ° C., a screw rotation speed of 25.5 rpm, and an extrusion rate of 20 kg / h, and a molding cycle of 27 seconds and an inner volume of 800 mL container with a weight of 120 g. was molded. The parison temperature was 223.9°C. The fine particle measurement described above was performed using the obtained container. As shown in Table 5, the number of fine particles of 0.1 µm or more was 12.4/mL.

Comparative example 2
Using an electric blow molding machine (manufactured by Tahara Co., Ltd.) in which a screw of shape B was inserted, the polyethylene was used in the same molding cycle as in Examples 1 and 2 under the conditions of set temperatures of 180 ° C. and 200 ° C. An attempt was made to mold a container, but as shown in Table 3, at 180°C and 200°C, even at a high screw rotation speed of 60 rpm, the extrusion rate of the polyethylene was small and did not reach 20 kg/h, so molding was impossible. Met. The parison temperatures when the polyethylene was extruded under conditions of set temperatures of 180° C. and 200° C. and a rotational speed of 60 rpm were 193.0° C., 212° C. and 2° C., respectively. Therefore, polyethylene 2 was extruded at a set temperature of 220° C., a screw rotation speed of 60.0 rpm, and an extrusion rate of 20 kg/h, and a container weighing 120 g and having an internal volume of 800 mL was molded in a molding cycle of 27 seconds. The parison temperature was 232.1°C. The fine particle measurement described above was performed using the obtained container. As shown in Table 5, the number of fine particles of 0.1 µm or more was 15.1/mL.

Claims (2)

In the method of manufacturing a container by blow molding a polyethylene resin, the polyethylene resin comprises a low molecular weight component having a density of 940 to 980 kg/m ³ and a high molecular weight component having a density of 920 to 950 kg/m ³ and a density lower than the low molecular weight component. The weight ratio of the two components is low molecular weight component: high molecular weight component = 20: 80 to 80: 20, has the following properties (1) to (5), and is a polyethylene resin Using a polyethylene resin having an ash content of 30 PPM or less relative to the resin and containing no additives ,
The screw shape of the blow molding machine satisfies the following conditions (1′) to (3′), and the temperature of the molten resin (parison) extruded by the screw is in the range of 170° C. to 210° C. A method for manufacturing a high-purity chemical container.
(1) Density (JIS K6922-1: 1997) is 940 to 970 kg/m ³
(2) Melt flow rate (JIS K6922-1: 1997) at 190°C and 21.6 kg load is 2.0 to 15 g/10 minutes
(3) The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) determined by gel permeation chromatography (GPC) is 8 to 15.
(4) In the molecular weight distribution curve obtained using gel permeation chromatography (GPC), the component with a molecular weight of 1000 or less is 0.50% by weight or less
(5) Chlorine content is 8 PPM or less for polyethylene resin
(1′) the ratio of the screw effective length L to the screw diameter D (L/D ratio) is in the range of 24 to 32
(2′) the groove depth of the screw in the supply portion is in the range of 0.1D to 0.3D
(3') The ratio of the groove depth of the supply portion to the groove depth of the compression portion is in the range of 0.80 to 1.00. 2. The method for producing a high-purity chemical container according to claim 1, wherein the number of fine particles of 0.1 μm or more eluted from the high-purity chemical container obtained by blow molding is 10/mL or less.