JP6206286B2 - Polyethylene for large high-purity chemical containers - Google Patents

Description

  The present invention relates to a polyethylene resin for high-purity chemical containers, and is particularly suitable for large-sized high-purity chemical containers, and has a small amount of polyethylene-derived fine particles and polymerization catalyst component-derived metal elution components in the stored and stored contents. The present invention relates to a polyethylene resin for high-purity chemical containers and a high-purity chemical container that are excellent in heat resistance and environmental stress crack resistance (ESCR).

In recent years, plasticization of various containers has been actively promoted for the purpose of reducing the weight and saving energy. As the plastic material, a polyolefin resin is generally used from the viewpoint of high strength, high weather resistance, high chemical resistance, environmental problems, and the like. Among polyolefin resins, polyethylene resin is particularly suitable as various molding resins. However, a cleaner polyethylene resin has been required for use of containers filled with high-purity contents. In particular, for polyethylene resins in pharmaceutical container applications, reagent container applications, and high-purity chemical container applications for semiconductors, cleaner polyethylene resins are required from the viewpoint of the purity of the contents to be filled. In addition to being required to be additive-free, it is necessary that the amount of ash derived from the polymerization catalyst or the like is small.
In particular, in the field of semiconductor manufacturing, high-purity chemicals such as various cleaning liquids, hydrofluoric acid, and hydrogen peroxide are used in processes such as wafer cleaning and etching. The demand for reduction of impurities and fine particles in chemicals is becoming stricter, and in order to satisfy this strict demand, the demand for cleaning containers filled with these chemicals is increasing year by year. In addition to the above requirements, there are increasing demands for increasing the size and durability of containers filled with these chemicals.

As a method for solving this problem, Patent Document 1 (Japanese Patent Laid-Open No. 11-080257) discloses that a melt flow rate with a density of 0.94 to 0.97 g / cm ³ , a temperature of 190 ° C., and a load of 21.6 kg is 2. -50 g / 10 min, 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, and the boiling normal hexane extract is 0 .1% by weight or less, and a polyethylene resin for high-purity chemical containers having a property that the chlorine content is 15 PPM or less with respect to the polyethylene resin has been proposed, but the improvement to the influence of the metal component derived from the polymerization catalyst component is said to be sufficient However, this does not necessarily mean that a satisfactory high-purity chemical container can be obtained.

In Patent Document 2 (Japanese Patent Laid-Open No. 11-080258), the density is 0.935 to 0.97 g / cm ³ , the temperature is 190 ° C., the melt flow rate at 21.6 kg load is 2 to 100 g / 10 minutes, from GPC. A high-purity chemical container having the properties that the ratio (Mw / Mn) of the required weight average molecular weight (Mw) and number average molecular weight (Mn) is 1.5 to 5, the ash content is 50 PPM or less, and the chlorine content is 5 PPM or less. Polyethylene resin has been proposed, but the improvement to the influence of the metal component derived from the polymerization catalyst component is not sufficient, and because Mw / Mn is small, the moldability is not necessarily good, and a satisfactory high-purity chemical container It does not mean that you can get.

In Patent Document 3 (Japanese Patent Laid-Open No. 11-080449), the density is 0.94 to 0.97 g / cm ³ , the temperature is 190 ° C., the melt flow rate at 21.6 kg load is 1 to 15 g / 10 minutes, from GPC. The required weight average molecular weight (Mw) and number average molecular weight (Mn) ratio (Mw / Mn) is 8 to 15, melt tension at 190 ° C. is 15 to 65 g, boiling normal hexane extract is 0.1% by weight or less, A polyethylene resin for large-sized high-purity chemical containers having a ash content of 50 PPM or less has been proposed, but the improvement to the influence of the metal component derived from the polymerization catalyst component is not sufficient, and it is produced by a two-stage polymerization method. The characteristics of the components to be obtained are not specific, and it does not necessarily mean that a satisfactory high-purity chemical container can be obtained.

Patent Document 4 (JP 2000-129044), a density of not more than 0.945 g / cm ³ or more 0.975g / cm ^3, _{I 2} is less than 0.05 g / 10min or more 30 g / 10min, A high-purity chemical comprising a polyethylene composition comprising 99 to 1 wt% of a specific property polyethylene produced by a metallocene catalyst by a slurry polymerization method and 1 to 99 wt% of a specific property polyethylene produced by a chromium catalyst by a slurry polymerization method However, the improvement to the influence of the metal component derived from the polymerization catalyst component is not sufficient, and it is not always possible to obtain a satisfactory high-purity chemical container.

In Patent Document 5 (Japanese Patent Laid-Open No. 2003-096133), a melt flow rate measured at a density of 0.95 to 0.97 g / cm ³ , a temperature of 190 ° C., and a load of 2.16 kg is 0.1 to 1 g / The value of the storage elastic modulus when the storage elastic modulus G ′ and the loss elastic modulus G ″ determined by dynamic viscoelasticity measurement (temperature 190 ° C., strain 10%) are equal for 10 minutes, the ash content is 15 ppm or less, A polyethylene resin for high-purity chemical containers characterized by having a property that G ₀ is 300,000 to 540000 dyn / cm ² has been proposed, but there is room for improvement with respect to low elution properties over a long period of the fine particle component.

Patent Document 6 (Japanese Patent Application Laid-Open No. 2008-179799) discloses a polyethylene resin composition produced using a Ziegler catalyst by a multistage polymerization method comprising at least a low molecular weight component and a syntactic component, and the low molecular weight component, the melt flow rate (JIS K7210-1999, code D) is 3 g / 10 min or more 50 g / 10 minutes or less, the density (JIS K7112-1999) is ethylene or less 960 kg / ^{m 3} or more 974kg / ^{m 3} alone A polymer or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, wherein a mass fraction of the high molecular weight component to the polyethylene resin composition is 0.40 or more and 0.46 or less, the polyethylene resin composition, density (JIS K7112-1999) is 955 kg / ^{m 3} or more 965 kg / ^{m 3} or less The melt flow rate (JIS K7210-1999, code T) is 0.40 g / 10 min or more and 1.0 g / 10 min or less, and is substantially free of additives. The polyethylene resin composition is proposed, but the improvement to the influence of the metal component derived from the polymerization catalyst component is not sufficient, and it is not necessarily possible to obtain a satisfactory high-purity chemical container.

Patent Document 7 (Japanese Patent Laid-Open No. 2010-242077) is a linear polyethylene comprising an ethylene homopolymer or an ethylene unit and one or two or more α-olefin units having 3 to 20 carbon atoms. It is a copolymer, has a density of 940 to 975 kg / m ³ , a melt flow rate of 0.1 to 20 g / 10 min at a temperature of 190 ° C. and a load of 2.16 kg, and Mw / Mn determined by GPC is It is 3.0 to 7.0, and the occupancy ratio of the component having a molecular weight of 1,000 or less obtained from the molecular weight distribution curve obtained by GPC is 1.0% by weight or less, and obtained from the molecular weight distribution curve obtained by GPC. The occupancy ratio of the component having a molecular weight of 1 million or more is 0.5% by weight or less, and there is one melting point peak of the endothermic curve obtained in the temperature rise measurement by the differential scanning calorimeter, A polyethylene for high-purity chemical containers has been proposed, wherein the amount of normal heptane extracted from is 1.0 wt% or less, and the amount of hydrocarbon components having 18 and 20 carbon atoms by ethanol extraction is 100 ppm or less. However, the improvement to the influence of the metal component derived from the polymerization catalyst component is not sufficient, and because Mw / Mn is small, the moldability is not necessarily good, and a satisfactory high-purity chemical container can be obtained. Absent.

Japanese Patent Laid-Open No. 11-080257 JP-A-11-080258 Japanese Patent Laid-Open No. 11-080449 JP 2000-129044 A JP 2003-096133 A JP 2008-179799 A JP 2010-2242077 A

  The purpose of the present invention is that there are few metal elution components derived from polyethylene resin-derived fine particles and polymerization catalyst components in the contents stored and stored, and excellent in moldability such as drawdown resistance and dischargeability during molding, And it is providing the high purity chemical container which shape | molded the polyethylene resin for high purity chemical containers excellent in the balance of ESCR / cleanness, and this polyethylene resin. In particular, an object of the present invention is to provide a polyethylene for a container that is suitable for a large container and has a small amount of fine particle components eluted from a filled chemical solution and a small amount of fine particles eluted over a long period of time.

  As a result of intensive studies to solve the above problems, the present inventors have found characteristics such as density, melt flow rate, molecular weight required by gel permeation chromatography (GPC), content of contained Ti and Al, etc. Found that by using polyethylene having a specific property, a large-sized high-purity chemical container excellent in moldability and ESCR can be obtained with few polyethylene-derived fine particles and metal-eluting components derived from polymerization catalyst components. Invented.

That is, according to 1st invention of this invention, 30-70 weight% of the following components (A) and 70-30 weight% of components (B) are contained, and the following (1)- (6), A polyethylene for high-purity chemical containers characterized by having the characteristics (8) to (10) is provided.
Component (A): an ethylene polymer having an HLMFR of 0.5 to 2 g / 10 min and a density of 0.941 to 0.945 g / cm ³ .
Component (B): an ethylene polymer having a melt flow rate (MFR) of 10 to 20 g / 10 minutes measured at a temperature of 190 ° C. and a load of 2.16 kg, and a density of 0.965 to 0.969 g / cm ³ .
Characteristic (1) Characteristic having a density of 0.940-0.960 g / cm ³ (2) Characteristic having a melt flow rate (HLMFR) measured at a temperature of 190 ° C. and a load of 21.6 kg of 5-15 g / 10 minutes (3) Measured by gel permeation chromatography (GPC), and the ratio of the detection area of the component having a molecular weight of 10,000 or less to the detection area of the whole polyethylene is 14.0% or less (4) Measured by GPC The ratio of the detection area of the component having a molecular weight of 1,000,000 or more to the detection area of the whole polyethylene is 7.0% or less.
Characteristic (5) The Ti content is 1.5 ppm by weight or less with respect to the whole polyethylene.
Characteristic (6) Al content is 3.0 ppm by weight or less with respect to the whole polyethylene
Characteristic (8) 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 more than 7.0 and 15.0 or less.
Characteristic (9) Fracture time (FNCT) at 80 ° C. and 1.9 MPa by full notch creep test is 100 hours or more
Property (10) Flexural modulus is 1200 MPa or more

According to a second aspect of the present invention, in the first invention, the high purity chemicals container polyethylene is provided, characterized by further satisfying the following characteristics (7).
Characteristic (7) Ash content is 15 ppm by weight or less

According to the third invention of the present invention, the polyethylene of the first or second invention is polymerized by multistage polymerization combining at least two polymerization reactors in the presence of a polymerization catalyst. A method for producing polyethylene for high-purity chemical containers is provided.

According to a fourth invention of the present invention, in the third invention, the polymerization catalyst for polyethylene is represented by the general formula Mg (OR ² ) _m X ² _2-m (wherein R ² is alkyl, aryl or A cycloalkyl group, X ² represents a halogen atom, m is 1 or 2, and a general formula Ti (OR ³ ) _n X ³ _4-n (wherein R ³ is alkyl, A homogeneous hydrocarbon solution containing a compound represented by the general formula AlR ¹ _l X ¹ _3-l: an aryl or cycloalkyl group, X ³ represents a halogen atom, and n is 1, 2 or 3. (Wherein R ¹ represents an alkyl, aryl, or cycloalkyl group, X ¹ represents a halogen atom, and l represents a number of 1 ≦ l ≦ 2). Obtained hydrocarbon-insoluble solid catalyst Process for producing a high purity chemical container polyethylene which is a catalyst containing an organoaluminum compound.

According to a fifth aspect of the present invention, there is provided a high-purity chemical container formed by molding the first or second polyethylene.

  The polyethylene of the present invention has few metal elution components derived from polyethylene resin-derived fine particles and polymerization catalyst components, is excellent in moldability such as draw-down resistance during molding and dischargeability, and is excellent in ESCR. A polyethylene resin for a pure chemical container can be obtained, and a high-purity chemical container having an excellent ESCR / clean balance can be formed without adding an additive. In particular, it is possible to provide a large-sized high-purity chemical container that is suitable for a large container and has a small elution amount of fine particle components with respect to a filled chemical solution and a small amount of fine particle elution over a long period of time.

The polyethylene of the present invention is a material suitable for a high-purity chemical container, particularly suitable for a large container, and is preferably suitable for a hollow container having an internal volume of 20 to 1000 L, more preferably 100 to 200 L. A high-purity chemical container refers to a container for containing chemicals with few impurities used in a semiconductor manufacturing process or the like.
The polyethylene for high-purity chemical containers of the present invention comprises an ethylene homopolymer or a copolymer of ethylene and another α-olefin, and the α-olefin is an α-olefin having 3 to 20 carbon atoms, such as propylene. 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, etc. Includes 1-butene and 1-hexene, more preferably 1-butene. These may be used alone or in combination of two or more.

  The polyethylene of the present invention can be obtained by polymerizing with a highly active catalyst such as a Ziegler type catalyst or a metallocene catalyst. Polymerization with a highly active Ziegler type catalyst is preferred. Examples of solid catalyst components in Ziegler type catalysts include titanium trichloride, vanadium trichloride, titanium tetrachloride or a catalyst component in which a halo alcoholate of titanium is supported on a magnesium compound, a coprecipitate or eutectic of a magnesium compound and a titanium compound And the like, and the like. In this, the solid catalyst component containing magnesium and titanium is preferable, and the catalyst system formed by combining the solid catalyst component and the organoaluminum compound is preferable.

Furthermore, as a polymerization catalyst for polyethylene of the present invention, general formula Mg (OR ² ) _m X ² _2-m (wherein R ² represents an alkyl, aryl or cycloalkyl group, X ² represents a halogen atom, m is 1 or 2) and the general formula Ti (OR ³ ) _n X ³ _4-n (wherein R ³ represents an alkyl, aryl or cycloalkyl group, and X ³ represents a halogen atom) A homogeneous hydrocarbon solution containing a compound represented by the general formula AlR ¹ _l X ¹ _3-l , wherein R ¹ is an alkyl, aryl or cycloalkyl group X ¹ represents a halogen atom, and l represents a number of 1 ≦ l ≦ 2, and includes a hydrocarbon-insoluble solid catalyst obtained by treatment with an organic aluminum halide compound and an organoaluminum compound. With catalyst Rukoto is preferred, it is preferable that further m = 2 and n = 3.

Examples of the polymerization method in the production of polyethylene using the polymerization catalyst system include a slurry polymerization method, a gas phase polymerization method, and a solution polymerization method. Among these, a slurry polymerization method using a polymerization solvent having 4 to 10 carbon atoms, for example, isobutane, isopentane, normal hexane, normal heptane, or the like is preferable, and a multistage polymerization method based on this polymerization method is preferably employed.
The ethylene polymer obtained by the above polymerization method preferably removes polyethylene (wax) having a low molecular weight dissolved in a solvent. Examples of the method for removing the wax include removal by a centrifugal separator, removal by washing with a solvent, and the like. By removing the wax, not only the contamination of the molding machine due to the wax during the molding process can be suppressed, but also the elution of the wax from the molded product can be suppressed.

  Hereinafter, the characteristics of the polyethylene of the present invention will be described.

Characteristic (1) Density:
The density of the polyethylene of the present invention is 0.940 to 0.960 g / cm ³ , preferably 0.945 to 0.955 g / cm ³ , more preferably 0.950 to 0.955 g / cm ³ . When the density is less than 0.940 g / cm ³ , the polymer component eluted from the molded container into the filled solution increases, and the cleanness of the inner solution is lowered and the rigidity is lowered. On the other hand, if the density exceeds 0.960 g / cm ³ , the impact resistance of the container is lowered and the ESCR is lowered.
The density can be measured according to JIS-K6922-1, 2: 1997.
A desired density can be obtained by changing the density depending on the kind and amount of the comonomer copolymerized with ethylene.

Characteristics (2) Melt flow rate (HLMFR) measured at a temperature of 190 ° C. and a load of 21.6 kg:
The HLMFR of the polyethylene of the present invention is 5 to 15 g / 10 minutes, preferably 6 to 13 g / 10 minutes, and more preferably 7 to 11 g / 10 minutes. When the HLMFR is less than 5 g / 10 min, the fluidity is lowered, the discharge performance is inferior, and the productivity of the container is hindered. On the other hand, if it exceeds 15 g / 10 minutes, the drawdown resistance is lowered, the container moldability is deteriorated, and the ESCR is lowered.
HLMFR can be measured according to JIS-K6922-2: 1997. HLMFR can be adjusted by the ethylene polymerization temperature, the use of a chain transfer agent, or the like, and a desired product can be obtained. That is, by increasing the polymerization temperature of ethylene and α-olefin, the HLMFR can be increased as a result of decreasing the molecular weight, and as a result of increasing the molecular weight by decreasing the polymerization temperature, the HLMFR can be decreased. Can do. Further, in the copolymerization reaction of ethylene and α-olefin, the amount of hydrogen to be coexisted (the amount of chain transfer agent) can be increased, and as a result of decreasing the molecular weight, HLMFR can be increased and the amount of hydrogen to coexist ( By reducing the amount of chain transfer agent, the HLMFR can be reduced as a result of increasing the molecular weight.

Characteristic (3) Ratio of the detection area of a component having a molecular weight of 10,000 or less to the detection area of the whole polyethylene, measured by gel permeation chromatography (GPC):
The polyethylene of the present invention is measured by GPC, and the ratio of the detection area of the component having a molecular weight of 10,000 or less to the detection area of the whole polyethylene is 14.0% or less, preferably 13.5% or less, more preferably 13 .3% or less. When the ratio exceeds 14.0%, the amount of fine particles eluted into the molded product increases, and the performance as a high-purity chemical container tends to decrease.
The said ratio can be calculated | required with the following method by gel permeation chromatography (GPC).
That is, it can be measured by gel permeation chromatography (GPC) under the following conditions.
Apparatus: WATERS 150C
Column: 3 AD80M / S manufactured by Showa Denko KK Measurement temperature: 140 ° C
Concentration: 1 mg / 1 ml
Solvent: o-dichlorobenzene Calculation of molecular weight and column calibration are performed according to the following method.
GPC chromatographic data is taken into a computer at a frequency of 1 point / second, and data processing is performed according to the description in Chapter 4 of “Size Exclusion Chromatography” published by Sadao Mori and Kyoritsu Publishing Co., Ltd.
The ratio can be adjusted by the type of catalyst, the type of cocatalyst, the polymerization temperature, the residence time in the polymerization reactor, the number of polymerization reactors, etc. However, it is preferable to remove the polymer obtained by polymerization using a centrifuge or washing with a solvent.

Characteristic (4) Ratio of detection area of components having a molecular weight of 1,000,000 or more with respect to the detection area of the whole polyethylene measured by GPC:
The polyethylene of the present invention is measured by GPC, and the ratio of the detection area of the component having a molecular weight of 1,000,000 or more to the detection area of the whole polyethylene is 7.0% or less, preferably 5.0% or less, more preferably Is 4.0% or less. When the ratio exceeds 7.0%, the resin unmelted component in the molded product increases, the inner surface becomes rough, and the inner surface area increases, resulting in an increase in the amount of fine particles eluted. The performance as a high purity chemical container tends to be lowered.
The said ratio can be calculated | required with the measuring method of molecular weight by said GPC.
The ratio can be adjusted by the type of catalyst, the type of cocatalyst, the polymerization temperature, the residence time in the polymerization reactor, the number of polymerization reactors, etc. Can be adjusted by

The polyethylene preferably further satisfies the following property (5).
Characteristic (5) Ti content:
In the polyethylene of the present invention, the Ti content is preferably 1.5 ppm by weight or less, more preferably 1.0 ppm by weight or less, and preferably 0.9 ppm by weight or less based on the whole polyethylene. If the ratio exceeds 1.0 ppm by weight, the amount of Ti eluted into the molded product increases, and the performance as a high-purity chemical container tends to decrease.
The content of Ti is about 0.5 g of a sample collected in a quartz beaker, 2 ml of sulfuric acid is added to the sample and heated to carbonize the sample, and then a colorless to pale yellow transparent solution is obtained while heating. Until "heating, allowing to cool, adding nitric acid" was repeated. After cooling, the volume is adjusted to 50 ml with pure water, further diluted 10 times, and the target metal element is measured by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) to obtain the concentration in the sample. It can be obtained by conversion.
The ratio can be adjusted by the type of catalyst, the type of promoter, and the like. As the catalyst, it is difficult to achieve the requirements of the present invention unless the activity is high, and a catalyst system comprising a combination of the above-described solid catalyst component containing magnesium and titanium and an organoaluminum compound is preferable.

The polyethylene preferably further satisfies the following property (6).
Characteristic (6) Al content:
In the polyethylene of the present invention, the Al content is preferably 3.0 ppm by weight or less, more preferably 1.0 ppm by weight or less, and preferably 0.85 ppm by weight or less based on the whole polyethylene. If the ratio exceeds 3.0 ppm by weight, the amount of Al eluted into the molded product increases, and the performance as a high-purity chemical container tends to decrease.
About 0.5 g of sample is collected in a quartz beaker, 2 ml of sulfuric acid is added and heated to carbonize the sample, and a colorless to pale yellow transparent solution is obtained while heating the sample. Until "heating, allowing to cool, adding nitric acid" was repeated. After cooling, the volume is adjusted to 50 ml with pure water, further diluted 10 times, and the target metal element is measured by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) to obtain the concentration in the sample. It can be obtained by conversion.
The ratio can be adjusted by the type of catalyst, the type of promoter, and the like. As the catalyst, it is difficult to achieve the requirements of the present invention unless the activity is high, and a catalyst system comprising a combination of the above-described solid catalyst component containing magnesium and titanium and an organoaluminum compound is preferable.

The polyethylene preferably further satisfies the following property (7).
Characteristic (7) Ash content is preferably 15 ppm by weight or less, more preferably 10 ppm by weight or less, and preferably 5 ppm or less.
When the ash content exceeds 15 ppm by weight, components derived from the ash content are eluted from the container of the molded product into the inner solution, which may reduce the cleanliness of the inner solution, and the performance as a high-purity chemical container tends to decrease. .
Ash content can be calculated | required based on JISK2272-1985.
The ash content can be adjusted by the type of catalyst, the type of promoter, and the like. As the catalyst, it is difficult to achieve this requirement unless the activity is high, and a catalyst system formed by combining the above-described solid catalyst component containing magnesium and titanium and an organoaluminum compound is preferable.

The polyethylene preferably further satisfies the following characteristics (8) to (10).
Characteristic (8) Ratio (Mw / Mn) of weight average molecular weight (Mw) and number average molecular weight (Mn) determined by gel permeation chromatography (GPC):
Mw / Mn calculated | required by GPC exceeds 7.0 and is 15.0 or less, Preferably it is 9-13, More preferably, it is 10-12.
The molecular weight, weight average molecular weight Mw, and number average molecular weight Mn can be measured by gel permeation chromatography (GPC) by the following method.
That is, it can be measured by gel permeation chromatography (GPC) under the following conditions.
Apparatus: WATERS 150C
Column: 3 AD80M / S manufactured by Showa Denko KK Measurement temperature: 140 ° C
Concentration: 1 mg / 1 ml
Solvent: o-dichlorobenzene Calculation of molecular weight and column calibration are performed according to the following method.
GPC chromatographic data is taken into a computer at a frequency of 1 point / second, data processing is performed according to the description in Chapter 4 of “Size Exclusion Chromatography” published by Sadao Mori and Kyoritsu Publishing Co., and Mw and Mn values are calculated.
Mw / Mn can be adjusted by the type of catalyst, the type of cocatalyst, the polymerization temperature, the residence time in the polymerization reactor, the number of polymerization reactors, etc. It can also be adjusted by the temperature, pressure, and cutting speed of the extruder. Preferably, it can be increased or decreased by adjusting the mixing ratio of the high molecular weight component and the low molecular weight component.
The Mw / Mn of the ethylene polymer is easily affected by the type of catalyst. In general, the molecular weight distribution is wide according to the Phillips catalyst, the molecular weight distribution is narrow according to the metallocene catalyst, and the intermediate molecular weight according to the Ziegler catalyst. A polymer having a distribution is obtained.

Characteristic (9) Fracture time at 80 ° C. and 1.9 MPa (FNCT) by full notch creep test:
The polyethylene of the present invention preferably has a breaking time (FNCT) at 80 ° C. and 1.9 MPa by a full notch creep test of 50 hours or more, more preferably 100 hours or more. When the FNCT is less than 50 hours, the durability as a product is low, and cracks easily occur in practice, and the performance as a container is not satisfied. Therefore, the performance as a high-purity chemical container tends to decrease.
FNCT can be measured by a full notched creep test (FNCT, 80 ° C., 1.9 MPa) in accordance with ISO DIS 16770. Here, the all notched creep test (FNCT) based on ISO DIS 16770 is an evaluation of long-term mechanical properties, and the sample is a razor blade on the entire circumference of a 6 mm × 6 mm × 11 mm prism. Prepare a test piece with a 1 mm notch and a cross section of 4 mm × 4 mm, and give the specimen a tensile stress corresponding to 1.9 MPa in pure water at 80 ° C. It is a value obtained by measuring the time until breakage.
The break time of FNCT can be adjusted by the molecular weight, density, and blending amount of the ethylene polymer, which is a high molecular weight component of polyethylene. Specifically, the molecular weight is increased and the density is decreased. By increasing the blending amount, the breaking time of the FNCT can be improved.

Characteristic (10) Flexural modulus:
The polyethylene of the present invention preferably has a flexural modulus of 1200 MPa or more, more preferably 1250 MPa or more. When the flexural modulus is less than 1200 MPa, the rigidity as a product is low, and the deformation at the time of filling with the internal liquid tends to occur practically, and the performance as a container is not satisfied. Therefore, the performance as a high-purity chemical container is not satisfied. The performance as a high purity chemical container tends to be lowered.
The flexural modulus is a value measured according to JIS-K6922-2: 1997, using a 4 × 10 × 80 mm plate-like body injection-molded at 210 ° C. as a test piece.
The flexural modulus can be adjusted by increasing or decreasing the molecular weight and density of polyethylene, and the flexural modulus can be increased by increasing the molecular weight or density.

The polyethylene of the present invention can be composed of a composition of a plurality of types of ethylene polymers, and the following component (A) is 30 to 70% by weight, preferably 40 to 60% by weight or less. (B) is 70 to 30% by weight, preferably 60 to 40% by weight.
Component (A): Ethylene polymer having an HLMFR of 0.5-2 g / 10 min and a density of 0.941-0.945 g / cm ³ Component (B): Melt flow rate at a temperature of 190 ° C. and a load of 2.16 Kg (MFR) 10 to 20 g / 10 min, density of 0.965 to 0.969 g / cm ³ ethylene polymer The polyethylene of the present invention is durable by using the composition of the above components and blending ratio. And rigidity (flexural modulus) can be improved, which is preferable as a high-purity chemical container.

  The polyethylene polymer contained in the polyethylene of the present invention can be produced by homopolymerization of ethylene alone or copolymerization of ethylene and α-olefin. The polyethylene-based polymer contained in the polyethylene of the present invention can be obtained by polymerizing by ordinary one-stage polymerization, but the polymerized components can be mixed under different conditions or can be produced as a composition by sequential multi-stage polymerization. it can.

The polyethylene of the present invention can be obtained by mixing the ethylene polymer of component (A) and the ethylene polymer of component (B). Also, for reasons such as the uniformity of the resin, those obtained by continuously polymerizing the ethylene polymer of component (A) and the ethylene polymer of component (B) (sequential multistage polymerization method) are preferable, For example, ethylene and α-olefin can be sequentially and continuously polymerized in a plurality of reactors connected in series.
In the present invention, the ethylene homopolymer is produced in at least one polymerization reactor by multistage polymerization in which the polyethylene component (A) and the component (B) are combined with at least two polymerization reactors in the presence of a polymerization catalyst. It is preferable that an ethylene copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms is polymerized at least in another polymerization reactor.

  Moreover, the composition which consists of a component (A) and a component (B) of this invention may mix after mixing a component (A) and a component (B) separately. Furthermore, each of the ethylene polymer of component (A) and component (B) can be composed of a plurality of components. The ethylene polymer may be a polymer successively polymerized in a multistage polymerization reactor using one type of catalyst, and may be produced in a single stage or multistage polymerization reactor using a plurality of types of catalysts. A polymer obtained by polymerizing using one kind or plural kinds of catalysts may be used.

  The polyethylene for high-purity chemical containers of the present invention can be made into a high-purity chemical container by molding into a container shape by a known molding method such as blow molding, injection molding, extrusion molding, or rotational molding. 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 as blow air is preferable for producing a clean container. The container shape and the capacity of the container are not particularly limited, but are preferably 20 to 1,000 L, more preferably 100 to 200 L.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In addition, the test method of an Example and a comparative example is as follows.
(1) Density: Measured according to JIS-K6922-1, 1997.
(2) HLMFR: Measured according to JIS-K6922-2: 1997.
(3) MFR: Measured according to JIS-K6922-2: 1997.
(4) Ratio of weight average molecular weight (Mw) and number average molecular weight (Mn) determined by gel permeation chromatography (GPC) (Mw / Mn): measurement of molecular weight, weight average molecular weight Mw, number average molecular weight Mn The following method was used. That is, it measured by the gel permeation chromatography (GPC) of the following conditions.
Apparatus: WATERS 150C
Column: 3 AD80M / S manufactured by Showa Denko KK Measurement temperature: 140 ° C
Concentration: 1 mg / 1 ml
Solvent: o-dichlorobenzene Calculation of molecular weight and column calibration were performed according to the following method.
GPC chromatographic data was loaded into a computer at a frequency of 1 point / second, and data processing was performed according to the description in Chapter 4 of “Size Exclusion Chromatography” published by Sadao Mori and Kyoritsu Publishing Co., and Mw and Mn values were calculated.
(5) Ratio of the detection area of the component having a molecular weight of 10,000 or less to the detection area of the whole polyethylene measured by GPC: It was determined by the molecular weight measurement method by GPC.
(6) Ratio of the detection area of components having a molecular weight of 1,000,000 or more to the detection area of the whole polyethylene measured by GPC: It was determined by the molecular weight measurement method using GPC.
(7) Ti content: About 0.5 g of a sample is collected in a quartz beaker, 2 ml of sulfuric acid is added to the sample and heated to carbonize the sample, and then a colorless to pale yellow transparent solution is heated. “Heating, allowing to cool, adding nitric acid” was repeated until it was obtained. After cooling, the volume is adjusted to 50 ml with pure water, further diluted 10 times, and the target metal element is measured by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) to obtain the concentration in the sample. Converted.
(8) Al content :: About 0.5 g of a sample was collected in a quartz beaker, 2 ml of sulfuric acid was added thereto and heated to carbonize the sample, and then heated to a colorless to pale yellow transparent solution. Was repeated until “heated, allowed to cool, and added nitric acid”. After cooling, the volume is adjusted to 50 ml with pure water, further diluted 10 times, and the target metal element is measured by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) to obtain the concentration in the sample. Converted.
(9) Ash content: Measured according to JIS K2272-1985.
(10) Fracture time (FNCT) at 80 ° C. and 1.9 MPa by full notch creep test: Measured by a full notched creep test (FNCT, 80 ° C., 1.9 MPa) in accordance with ISO DIS 16770.
(11) Flexural Modulus: using a plate-like body 4 × 10 × 80 mm was injection molded at 210 ° C. As test pieces, JIS-K6922-2: was measured in accordance with 1997.

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(12) Large blow moldability:
(I) Discharge amount, motor load: Discharge amount per hour at a temperature of 200 ° C., a screw rotation speed of 40 rpm, a die diameter of 18 mm, and a core diameter of 15 mm, using a TP-5 manufactured by Tahara, a small multilayer blow molding machine The resin pressure was measured. The case where the discharge amount was 15 kg / hr or more and the resin pressure was 25 MPa or less was designated as “◯”, and the others were designated as “X”.
(Ii) Drawdown rate: Under the same conditions as the dischargeability, the time for the parison length to reach 12 cm and 60 cm was measured, and the drawdown rate was calculated by the following formula.
Drawdown rate = (time for the parison length to reach 60 cm) / (time for the parison length to reach 12 cm)
Those with a drawdown rate of 4.5 or more were marked with “◯” and those with a drawdown rate of “x”.

(13) Evaluation of molded product (iii) Cleanness-fine particle elution: The blow-molded internal volume 500 cc bottle is used in a clean room with water (EL ammonia water for electronic industry manufactured by Mitsubishi Chemical; 29% ammonia aqueous solution). After washing 5 times, the container was filled with water and allowed to stand for 3 months, and then the number of fine particles of 0.2 μm or more was measured with a KL-25 type liquid fine particle counter manufactured by Lion. The case where the number of fine particles was 100 / ml or less was designated as “◯”, and the case where the fine particles were other than “×”.
(Iv) Cleanness-metal elution: After the above blow molded 500 cc bottle is washed 5 times with water in a clean room, the container is filled with water and left for 3 months, and then the Ti and Al concentrations are measured. went. The case where the metal elution amount was 10 weight ppb or less was designated as “◯”, and the others were designated as “x”.

Example 1
(A) Preparation of solid catalyst 575 g of Mg (OEt) ₂ , 755 g of Ti (OBu) ₃ Cl and 185 g of n-C ₄ H ₉ OH were mixed at 150 ° C. for 6 hours to homogenize, and after cooling, normal hexane Was added to make a uniform solution. Next, 2285 g of ethylaluminum sesquichloride was dropped at a predetermined temperature and stirred for 1 hour. Furthermore, washing with normal hexane was repeated to obtain 1100 g of a solid catalyst.
(B) Polymerization of ethylene Using the solid catalyst, continuous polymerization was performed using an apparatus in which two 0.6 m ³ reactors were connected in series. The first polymerization tank was continuously supplied with normal hexane 70 kg / hour, triethylaluminum 1.4 g / hour, the solid catalyst component 0.67 g / hour, ethylene 31 kg / hour, and hydrogen continuously. Continuous polymerization was carried out while maintaining hydrogen in the gas phase at 1.1 ° C./mol in terms of ethylene concentration ratio. The MFR of the polymer obtained in the first polymerization tank at 190 ° C. under a load of 2.16 kg was 15 g / min. The polymer slurry of the first polymerization tank is continuously supplied to the second polymerization tank, and 47 kg / hour of normal hexane and 31 kg / hour of ethylene are continuously supplied, the polymerization temperature is 80 ° C., and hydrogen in the gas phase Was maintained at 0.08 mol / mol with respect to ethylene and butene was maintained at 0.023 mol / mol with respect to ethylene to carry out the second stage polymerization. The obtained polymerization slurry was subjected to solid-liquid separation with a centrifuge , passed through a drying step, pelleted with a 40 mmφ extruder without using any additives, and measured for physical properties. The results of physical property measurement are shown in Table 1.
(C) Molding of container The polyethylene resin obtained above is TP-5 manufactured by Tahara, a small multilayer blow molding machine, and the pinch-off length is 95% of the bottom diameter at a temperature of 200 ° C. and a screw rotation speed of 40 rpm. Thus, a 500 cc bottle was molded while appropriately selecting a die core. Table 1 shows the evaluation results of the blow moldability and the evaluation results of the molded product.

Comparative Example 1
A commercially available high-density polyethylene (HLMFR = 7 g / 10 min, density = 0.554 g / cm ³ ) was used and the blow molded container was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the resin and the evaluation results of the container.

Comparative Example 2
In the polymerization of ethylene in Example 1 (B), as the first stage polymerization conditions, hydrogen was 2.1 mol / mol in terms of ethylene, and as the second stage polymerization conditions, hydrogen was 0 in terms of ethylene concentration. A polyethylene resin and its blow-molded container were obtained in the same manner as in Example 1 except that 12 mol / mol and butene were used in an ethylene concentration of 0.02 mol / mol. Table 1 shows the physical properties of the resin and the evaluation results of the container.
Comparative Example 3
According to Example 1 of JP-A-11-80257, a polyethylene resin was produced, and a blow molded container was obtained in the same manner as Example 1. Table 1 shows the physical properties of the resin and the evaluation results of the container.

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As is apparent from Table 1, containers made of polyethylene having properties such as density, melt flow rate, and molecular weight satisfying the requirements of the present invention were excellent in large blow moldability and excellent in rigidity, FNCT, and cleanliness of the container. (Example 1). On the other hand, the area ratio of components having a molecular weight of 10,000 or less measured by GPC, the area ratio of components having a molecular weight of 1,000,000 or more, Ti content, and Al content measured by GPC deviate from the requirements of the present invention. And the fine particle elution property and metal elution property of a molded article became large (comparative example 1). Moreover, when HLMFR deviated from the requirement of the present invention, it was a result that large blow moldability deteriorated (Comparative Example 2).

  According to the present invention, since there are few metal elution components derived from polyethylene resin-derived fine particles and polymerization catalyst components, and excellent in moldability such as drawdown resistance and dischargeability during molding, and excellent in durability, It can be used as a polyethylene resin for high-purity chemical containers, and a high-purity chemical container excellent in durability / cleanness balance can be formed. In particular, since it is suitable for a large container and can provide a large-sized high-purity chemical container with a small amount of fine particle components eluted with respect to a filled chemical solution and a small amount of fine particle elution over a long period of time, It is very useful in industry.

Claims (5)

It contains 30 to 70% by weight of the following component (A) and 70 to 30% by weight of component (B), and has the following characteristics (1) to (6) and (8) to (10). Characteristic polyethylene for high-purity chemical containers.
Component (A): an ethylene polymer having an HLMFR of 0.5 to 2 g / 10 min and a density of 0.941 to 0.945 g / cm ³ .
Component (B): an ethylene polymer having a melt flow rate (MFR) of 10 to 20 g / 10 minutes measured at a temperature of 190 ° C. and a load of 2.16 kg, and a density of 0.965 to 0.969 g / cm ³ .
Characteristic (1) Characteristic having a density of 0.940-0.960 g / cm ³ (2) Characteristic having a melt flow rate (HLMFR) measured at a temperature of 190 ° C. and a load of 21.6 kg of 5-15 g / 10 minutes (3) Measured by gel permeation chromatography (GPC), and the ratio of the detection area of the component having a molecular weight of 10,000 or less to the detection area of the whole polyethylene is 14.0% or less (4) Measured by GPC The ratio of the detection area of the component having a molecular weight of 1,000,000 or more to the detection area of the whole polyethylene is 7.0% or less.
Characteristic (5) The Ti content is 1.5 ppm by weight or less with respect to the whole polyethylene.
Characteristic (6) Al content is 3.0 ppm by weight or less with respect to the whole polyethylene
Characteristic (8) 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 more than 7.0 and 15.0 or less.
Characteristic (9) Fracture time (FNCT) at 80 ° C. and 1.9 MPa by full notch creep test is 100 hours or more
Property (10) Flexural modulus is 1200 MPa or more The polyethylene for high-purity chemical containers according to claim 1, wherein the polyethylene further satisfies the following property (7).
Characteristic (7) Ash content is 15 ppm by weight or less The method for producing polyethylene for high-purity chemical containers according to claim 1 or 2, wherein the polyethylene is polymerized by multistage polymerization in which at least two polymerization reactors are combined in the presence of a polymerization catalyst . The polyethylene polymerization catalyst has the general formula Mg (OR ² ) _m X ² _2-m (wherein R ² represents an alkyl, aryl or cycloalkyl group, X ² represents a halogen atom, and m represents 1 or 2). And a compound represented by the general formula Ti (OR ³ ) _n X ³ _4-n (wherein R ³ represents an alkyl, aryl or cycloalkyl group, X ³ represents a halogen atom, and n represents 1 A homogeneous hydrocarbon solution containing a compound represented by the formula: AlR ¹ _l X ¹ _3-l (wherein R ¹ represents an alkyl, aryl or cycloalkyl group, and X ¹ Represents a halogen atom, and l represents a number of 1 ≦ l ≦ 2, and is a catalyst containing a hydrocarbon-insoluble solid catalyst obtained by treatment with an organic aluminum halide compound and an organoaluminum compound. Features and Process for producing a high purity chemical containers for polyethylene according to claim 3 that. A high-purity chemical container obtained by molding the polyethylene according to claim 1 or 2.