JP5145911B2 - Polyethylene resin composition and blow container comprising the same - Google Patents

Description

  The present invention relates to a polyethylene resin composition and a blow container comprising the same, and more specifically, in the semiconductor device industry field, the precision industrial parts field, etc., for example, a high-purity chemical used for cleaning parts. The present invention relates to a polyethylene resin composition for large blow molding, which is suitable for containers, particularly when the skin of the product and the impact strength of the product are good and a high-purity chemical is filled, and the generation of fine particles in the chemical is small.

  In general, food containers such as detergent bottles, beverage bottles and edible oil bottles, large containers such as drum cans and industrial cans, and blow containers such as kerosene cans and fuel containers such as gasoline tanks are manufactured by a hollow molding method. In the hollow molding method, the resin is melted by an extruder and extruded into a cylindrical parison, and the parison is expanded and deformed by blowing a pressurized gas from a blow pin with the extruded parison sandwiched between molds. It cools after shaping into a cavity shape. These hollow molding methods can be widely applied to hollow molded products such as bottles, gasoline tanks with complex shapes, drum cans, and panel-shaped molded products. It is widely used because the molding cost is low.

  The demand for blow containers, particularly high-purity chemical containers, is rapidly increasing with the recent remarkable development of the electronics industry. High-purity chemicals are used as chemicals indispensable for the manufacture of electronic circuits such as large-scale and integrated LSIs. For example, sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, ammonium fluoride for wafer cleaning / etching, wiring / insulating film etching, jig cleaning, developer, resist dilution, resist stripping solution, drying, etc. , Hydrogen peroxide solution, isopropyl alcohol, xylene, TMAH (tetramethylammonium hydroxide), methanol, acetic acid, phosphoric acid, aqueous ammonia, PGMEA (propylene glycol methyl ether acetate), DMSO (dimethyl sulfoxide), NMP (N-methyl) 2-pyrrolidone), ECA (ethyl carbamate), ethyl lactate and the like 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. When hollow molding a large product, there is a tendency for the parison to hang down due to its own weight (drawdown). In order to reduce this drawdown, it is necessary to use a resin having a sufficiently high melt viscosity and melt tension. Conventionally, a method of increasing the molecular weight has been taken to improve the drawdown resistance of polyethylene, but the melt viscosity becomes high, the extrusion characteristics (extrusion amount, parison surface state) deteriorate, and the parison fusion property is poor. Therefore, there is a problem that the pinch-off shape is deteriorated. As a method for solving this problem, a multi-stage polymerization method (see Patent Document 1), a method of adding a crosslinking agent (see Patent Document 2), and a method of mixing two-component polyethylene at a specific ratio (Patent Document) 3), a method of adding a fluorine-based polymer (see Patent Document 4), and the like are known.

  In recent years, instead of the accumulator type molding machine conventionally used in large hollow molding machines, a continuous extrusion type hollow molding machine with few stagnant parts has begun to be used. Compared to the accumulator method, a continuous extrusion type hollow molding machine takes a long time to extrude the parison, easily causes the parison to be drawn down, and is required to have a resin having more excellent draw-down resistance. For this reason, polyethylene improved by the above-described conventional methods has insufficient draw-down resistance to obtain large blow products, product skin is deteriorated, and there are many metal residues and is not suitable for high-purity chemical containers. It is.

JP-A-55-152735 Japanese Patent Publication No. 2-52654 JP-A-6-299909 Japanese Patent Laid-Open No. 11-181171

  An object of the present invention is to provide a polyethylene resin composition suitable for a large blow container having both a product appearance and impact resistance, which are disadvantages of a conventional polyethylene blow container, and having reduced ash content.

  As a result of intensive studies on the above problems, the present inventors have found that a polyethylene resin composition consisting of a polyethylene resin and a fluoropolymer and satisfying specific requirements is particularly suitable for a large blow container. The present invention has been completed.

That is, the present invention comprises a polyethylene resin comprising 99.80 to 99.99% by weight of a polyethylene resin and 0.01 to 0.2% by weight of a fluorine polymer, and satisfying the following requirements (a) to (h): The present invention relates to a composition and a blow container comprising the same.
(A) Based on JIS K6922-1 (1997), the density measured by a density gradient tube method is 940 to 970 kg / m ³ ,
(B) Under the condition of 190 ° C. and 21.6 kg load, the melt flow rate (HLMFR) in accordance with JIS K7210 (1999) is 1 to 15 g / 10 min.
(C) The weight average molecular weight (Mw) / number average molecular weight (Mn) obtained as a linear polyethylene conversion value from gel permeation chromatography (GPC) is 6 to 15,
(D) Using a die having a length / diameter = 8 mm / 2.095 mm, a melt tension (MS) measured at 190 ° C., a piston lowering speed of 10 mm / min, and a draw ratio of 47 is 150 to 600 mN,
(E) Charpy impact strength measured according to JIS K6922-2 (1997) is 50 kJ / m ² or more,
(F) Environmental stress cracking measured in accordance with JIS K6922-2 (1997) is 100 hours or more,
(G) Surface roughness when measuring the surface of a strand extruded under the conditions of 190 ° C. and a shear rate of 50 s ⁻¹ according to JIS B0601 using a die of length / diameter = 8 mm / 2.095 mm. 5 μm or less,
(H) Ash content is 80 ppm or less Hereinafter, the present invention will be described in detail.

  The polyethylene resin composition of the present invention comprises a polyethylene resin and a fluoropolymer, and satisfies the requirements (a) to (h) above. In addition, the container has a reduced ash content, and is particularly suitable for a container for high-purity chemicals in which contamination of foreign matters such as fine particles is regarded as a problem. The polyethylene resin composition of the present invention is suitable for blow molding, and particularly suitable for blow molding for large containers and continuous extrusion blow molding.

  As the polyethylene resin constituting the polyethylene resin composition of the present invention, the polyethylene resin composition of the present invention, that is, the polyethylene resin composition constituting the above requirements (a) to (h) is configured. Can be used without any limitation as long as it is a polyethylene-based resin, such as an ethylene homopolymer, an ethylene-α-olefin copolymer, a high-pressure method low-density polyethylene, and the like. A mixture of these may also be used.

  Here, when the polyethylene resin is an ethylene-α-olefin copolymer, examples of the α-olefin at that time include propylene, 1-butene, 4-methyl-1-pentene, 1-pentene, 1-pentene, and the like. Hexene, 1-octene, 1-nonene, 1-decene, 1-hexadecene, 1-octadecene and the like can be mentioned. As the highly active polymerization catalyst at that time, Kaminsky mainly composed of Ziegler catalyst, metallocene, etc. What is called a type catalyst is suitable. As a specific example, a Ziegler catalyst includes a catalyst comprising a solid catalyst component essentially containing titanium, magnesium and halogen and an organoaluminum compound. For example, a combination of a metallocene compound (transition metal compound) mainly composed of a transition metal such as titanium, zirconium or hafnium and an ionic compound or clay mineral that reacts with an organometallic compound or a metallocene compound to form a stable anion. A generally known polymerization catalyst system consisting of can be used. The Kaminsky catalyst may be used alone or in combination. Examples of the metallocene compound include bis (cyclopentadienyl) titanium dichloride, bis (cyclopentadienyl) zirconium dichloride, bis (cyclopentadienyl) hafnium dichloride, bis (indenyl) titanium dichloride, bis (indenyl) zirconium dichloride, Bis (indenyl) hafnium dichloride, ethylenebis (indenyl) titanium dichloride, ethylenebis (indenyl) zirconium dichloride, ethylenebis (indenyl) hafnium dichloride, diphenylmethylene (cyclopentadienyl) (9-fluorenyl) zirconium dichloride, etc. For example, trimethylaluminum, triethylaluminum, triisopropyl Examples of ionic compounds that react with transition metal compounds to form stable anions include lithium tetrakis (pentafluorophenyl) borate, N, N-dimethylanilinium tetrakis (pentafluorophenyl) borate, and the like. Examples of clay minerals include montmorillonite, hectorite, and saponite.

  In addition, the polymerization method at that time is not particularly limited, and any of a general polymerization method such as a gas phase method, a slurry method, a solution method, and a high pressure method may be used. Moreover, what was multistage-polymerized by 1 step | paragraph or 2 steps | paragraphs or more can be manufactured also by mechanically blending 2 or more types of polymers.

  And since it becomes possible to set it as the polyethylene-type resin composition with especially small ash content, it is preferable that it is the polyethylene-type resin manufactured using the Ziegler type polymerization catalyst or metallocene polymerization catalyst which is a highly active polymerization catalyst.

  In particular, since the polyethylene resin composition of the present invention can be obtained efficiently, the polyethylene resin itself is preferably a polyethylene resin that satisfies the requirements (a) to (h). For example, (trade name) Nipolon Hard 9D03E, 9D03G (manufactured by Tosoh Corporation) can be obtained as commercial products.

  Those corresponding to Nipolon Hard 9D03E and 9D03G can be produced by the following two-stage polymerization method.

  Ziegler catalyst mainly composed of Al, Ti, Mg and Cl prepared according to JP-A-7-41513 and a solvent (hexane), ethylene (concentration 4-6 g / kg-solvent), hydrogen (concentration 0.05- 0.07 g / kg-solvent) and triisobutylaluminum (concentration 0.10-0.20 g / kg-solvent) are continuously fed to the first stage polymerization vessel, temperature 80-90 ° C., total pressure 2,800 kPa, Ethylene polymerization (low molecular weight component) is carried out in a hexane slurry under conditions of an average residence time of 1.5 to 2.0 hours. The hexane slurry containing the first stage polymer is continuously supplied to another second stage polymerizer after removing unreacted hydrogen and ethylene in a flash tank. In the second stage polymerization apparatus, ethylene (concentration 8 to 10 g / kg-solvent), hydrogen (concentration 4 to 6 g / kg-solvent), 1-butene (concentration 0.5 to 2.2 g / kg-solvent) And ethylene polymerization (high molecular weight component) is carried out under conditions of a temperature of 75 to 85 ° C., a pressure of 1,500 kPa, and an average residence time of 1.5 to 2.0 hours. After the hexane slurry of the second stage polymerizer is sent to a flash tank to remove unreacted hydrogen, ethylene, and 1-butene, a mixture powder of an ethylene-based copolymer can be obtained through a drying process. The polymerization rate of the low molecular weight component is 50% by weight, and the polymerization rate of the high molecular weight component is 50% by weight.

  Nipolon hard 9D03E and Nipolon hard 9D03G equivalent products can be obtained by granulating the two-stage polymerized powder in the above manufacturing process without adding any additives.

  In order to increase the melt tension, increase the Charpy impact strength, or strengthen the environmental stress crack resistance, the ratio of the low molecular weight component to the high molecular weight component is changed, and the polymerization ratio of the low molecular weight component is set to 20-80. Examples thereof include a method in which the polymerization rate of the high molecular weight component is 80 to 20% by weight and a method in which the molecular weight of the low molecular weight component and the high molecular weight component is increased.

  As the fluorine-based polymer constituting the polyethylene-based resin composition of the present invention, any polymer can be used as long as it belongs to the category of the fluorine-based polymer, such as vinylidene fluoride, vinyl fluoride, tetrafluoroethylene, Fluorinated olefin homopolymers and copolymers typified by hexafluoropropylene can be mentioned. Among them, especially when subjected to molding processing, it has both product appearance and impact resistance, and is a polyethylene type for large blow containers Since it becomes a resin composition, a vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer is preferable. Fluoropolymers are commercially available in which a fluorine-based polymer component is blended with an inorganic anti-blocking agent, but when an anti-blocking agent is blended, the amount of ash increases and the generation of fine particles increases. The blending amount of the anti-sticking agent is preferably 5% by weight or less, particularly preferably 1% by weight or less. As the fluoropolymer, for example, (trade name) Dynamer FX5911X (manufactured by Sumitomo 3M Co., Ltd.) or the like can be obtained as a commercial product.

  The polyethylene-based resin composition of the present invention is composed of 99.80 to 99.99% by weight of the polyethylene-based resin and 0.01 to 0.2% by weight of a fluoropolymer, and particularly when subjected to a molding process. Since it has both product appearance and impact resistance, and becomes a polyethylene resin composition for large blow containers, from 99.90 to 99.98 wt% of the polyethylene resin and 0.02 to 0.1 wt% of the fluoropolymer. It is preferable to become. Here, when the fluorine-based polymer is less than 0.01% by weight, the molded product when the obtained composition is subjected to blow molding becomes rough. On the other hand, when the fluorine-based polymer exceeds 0.1% by weight, not only the raw material cost increases, but the resulting composition tends to increase the ash content.

The polyethylene resin composition of the present invention is (a) based on JIS K6922-1 (1997), and has a density measured by a density gradient tube method of 940 to 970 kg / m ³ , particularly 945 to 965 kg / m ³ . Preferably there is. Here, when the density is less than 940 kg / m ³ , components that are likely to be eluted in the chemical increase, and there may be a problem in using it for a high-purity chemical when it is used as a container. On the other hand, when the density exceeds 970 kg / m ³ , the stress cracking resistance is lowered.

  The polyethylene resin composition of the present invention has a melt flow rate (hereinafter referred to as HLMFR) in accordance with JIS K7210 (1999) of 1 to 15 g / 10 min under the conditions of (b) 190 ° C. and 21.6 kg load. In particular, 2 to 10 g / 10 min is preferable. Here, when the HLMFR is less than 1 g / 10 min, the melt viscosity becomes too high, so that not only the extrusion load during the molding process becomes high, but also the product becomes rough. On the other hand, when the HLMFR exceeds 15 g / 10 minutes, the melt tension becomes small and the drawdown during the molding process becomes severe and the molding processability is inferior, and the resulting product is inferior in impact strength. In addition, HLMFR as used in the field of this invention can be measured based on the conditions G (190 degreeC, 21.6kg load) of the appendix A of JISK7210 (1999), for example.

  The polyethylene-based resin composition of the present invention has a weight average molecular weight / number average molecular weight (hereinafter referred to as Mw / Mn) determined as (c) linear permeation chromatography by gel permeation chromatography (6). It is 15 and it is especially preferable that it is 8-12. Here, when Mw / Mn is less than 6, since the melt viscosity becomes too high, not only the extrusion load at the time of molding is increased, but also the product is roughened. On the other hand, when Mw / Mn exceeds 15, the product obtained is inferior in impact strength.

  The polyethylene-based resin composition of the present invention has (d) a melt tension measured using a die having a length / diameter = 8 mm / 2.095 mm under measurement conditions of 190 ° C., a piston lowering speed of 10 mm / min, and a draw ratio of 47. Hereinafter, it is described as MS.) Is 150 to 600 mN, and particularly preferably 200 to 300 mN. Here, when MS is less than 150 mN, not only the drawdown during the molding process is severe and the molding processability is inferior, but also the resulting product is inferior in impact strength. On the other hand, when MS exceeds 600 mN, fluidity | liquidity falls and it becomes inferior to shaping | molding workability. The MS referred to in the present invention is, for example, a capillary viscometer (Toyo Seiki Seisakusho, trade name: Capillograph) having a barrel diameter of 9.55 mm, a length (L) of 8 mm, a diameter (D) of 2.095 mm, and an inflow angle of A 90 ° die is mounted, the temperature is set to 190 ° C., the piston lowering speed is set to 10 mm / min, and the stretch ratio is set to 47 for measurement.

The polyethylene-based resin composition of the present invention has a Charpy impact strength measured in accordance with (e) JIS K6922-2 (1997) of 50 kJ / m ² or more, and particularly preferably 60 kJ / m ² or more. Here, when the Charpy impact strength is less than 50 kJ / m ² , the drop strength when manufactured is inferior.

  The polyethylene resin composition of the present invention has an environmental stress crack resistance measured in accordance with (f) JIS K6922-2 (1997) of 100 hours or more, and particularly preferably 150 hours or more. Here, when the environmental stress crack is less than 100 hours, when the product is used as a container, problems are likely to occur during long-term storage and repeated use due to the influence of the residual strain of the contents and the molded container. The environmental stress-resistant crack referred to in the present invention is, for example, in accordance with JIS K6922-2 (1997), using a constant temperature bath of 50 ± 0.5 ° C., and cracking 10 samples in a 10 wt% solution of Nonion NS210. It can be measured by measuring the time until the occurrence of, and calculating the F50 value.

The polyethylene resin composition of the present invention uses (g) a die having a length / diameter = 8 mm / 2.095 mm, and a strand extruded under conditions of 190 ° C. and a shear rate of 50 s ⁻¹ in accordance with JIS B0601. The surface roughness (hereinafter referred to as Ra) when the surface is measured is 5 μm or less, and particularly preferably 2 μm or less. Here, when Ra exceeds 5 micrometers, when it is set as a product, it becomes inferior in an external appearance (surface skin). In the present invention, for example, Ra is a capillary viscometer (Toyo Seiki Seisakusho, trade name: Capillograph) having a barrel diameter of 9.55 mm, a length (L) of 8 mm, a diameter (D) of 2.095 mm, and an inflow angle. A 90 ° die is mounted, the strand is extruded at a temperature of 190 ° C. and a shear rate of 50 s ⁻¹ . The surface roughness Ra value of the extruded strand can be measured using a digital microscope (Ultra Deep Shape Measuring Microscope VK-8550 manufactured by Keyence Corporation) in accordance with JIS B0601.

  The polyethylene resin composition of the present invention has (h) an ash content of 80 ppm or less, particularly preferably 50 ppm or less. Here, when the amount of ash exceeds 80 ppm, it becomes easy to generate the problem that ash is eluted in the contents when a product such as a container is used. Examples of the ash include residues of polyethylene-based resin polymerization catalysts such as Al, Mg, Ti and Si, metal-containing additives such as neutralizing agents, impurities and attachments during the production of polyethylene-based resins or polyethylene-based resin compositions. Examples thereof include metal oxides of kimonos. The amount of ash in the present invention refers to, for example, the crucible containing the sample is red-heated on the burner to burn the polymer, and then heated in an electric furnace to completely ash until the weight of the crucible reaches a constant weight. . After the crucible is cooled in a desiccator, it can be measured by determining the amount of ash from the weight difference of the crucible before and after ashing.

  In addition, the polyethylene resin composition of the present invention supplements chlorine generated from the polymerization catalyst when producing the polyethylene resin, and prevents corrosion of the molding machine and mold during the molding process, and when used as a product. It is preferable to further contain 0.01 parts by weight or less of hydrotalcite with respect to 100 parts by weight of the total amount of the polyethylene resin and the fluorine-based polymer.

  The polyethylene-based resin composition of the present invention is an additive such as an antioxidant, a weathering stabilizer, an antistatic agent, a lubricant, an antiblocking agent, a cross-linking agent, an organic / inorganic pigment, etc. May be blended.

  As a method for producing the polyethylene resin composition of the present invention, any method can be used as long as the polyethylene resin composition can be produced. For example, a method of directly adding in the pellet granulation step after polymerization. Moreover, a method of preparing a high-concentration master batch in advance and dry blending it at the time of molding can be mentioned.

  When the polyethylene resin composition of the present invention is used as a product, particularly when the product skin and the impact strength of the product are good and high-purity chemicals are filled, there is little generation of fine particles in the chemicals. In particular, it is suitable as a large blow container having an internal volume of 50 liters or more and a container for high-purity chemicals.

  The production method when the polyethylene resin composition of the present invention is used as a blow container is not particularly limited. For example, an accumulator type or continuous extrusion type extrusion blow molding method, injection blow molding method, extrusion stretch blow molding method, injection The stretch blow molding method can be mentioned. Among them, there is little resin retention in the extruder and in the crosshead, there is little resin deterioration, and the effect of improving the skin of the product by adding a fluoropolymer is large. An extrusion blow molding method is preferred. Examples of the parison method include a cold parison method and a hot parison method, and are not particularly limited. For example, the polyethylene resin of the present invention is put into a blow molding machine (manufactured by Nippon Steel Works) having a 115 mmφ extrusion screw set at 220 to 230 ° C., and the parison is continuously extruded at a screw rotation speed of 30 rpm, and is set at 25 ° C. It is obtained by sandwiching with a mold and blowing air from a blow pin and cooling for 60 seconds.

  Moreover, when using the blow container of this invention as a high purity chemical | medical agent container, it can be made into a single layer or a multilayer. In this case, the structure of the layer is not particularly limited, but it is effective to use the present polyethylene resin for the innermost layer. In multilayer molding, for example, gas barrier properties can be imparted by coextrusion of the intermediate layer as EVOH (ethylene / vinyl alcohol copolymer resin) or polyamide.

  The blow container of the present invention can be used for large-sized blow containers of 50 liters or more, such as cleaning and etching of parts in the field of semiconductor devices and precision industrial parts, and containers of high purity solvents required for medical and food use. It is preferably used.

  Compared with conventional polyethylene containers, the blow container of the present invention has a good product skin, excellent impact strength, and can stably maintain its mechanical strength for a long period of time. In the industrial parts field, etc., it is suitably used for parts such as cleaning and etching of parts, high purity solvent containers and large containers required for medical use and food use.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

  Furthermore, various physical properties of the polyethylene resins in Examples and Comparative Examples were measured by the methods shown below.

~density~
The density was measured by a density gradient tube method in accordance with JIS K6922-1 (1997).

~ HLMFR ~
HLMFR was measured in accordance with the condition G (190 ° C., 21.6 kg load) in Annex A of JIS K7210 (1999).

~ Molecular weight distribution ~
The weight average molecular weight (M _w ) and number average molecular weight (M _n ) were measured by gel permeation chromatography (GPC). Tosoh Co., Ltd. HLC-8121GPC / HT is used as the GPC apparatus, Tosoh Co., Ltd. TSKgel GMHhr-H (20) HT is used as the column, the column temperature is set to 140 ° C., and 1 is used as the eluent. Measurement was performed using 2,4-trichlorobenzene. A measurement sample was prepared at a concentration of 1.0 mg / mL, and 0.3 mL was injected and measured. The calibration curve of molecular weight is calibrated using a polystyrene sample having a known molecular weight. In addition, _Mw and _Mn were calculated | required as a value of linear polyethylene conversion.

~ Melting tension (MS) ~
The melt tension (MS) is a capillary viscometer (Toyo Seiki Seisakusho, trade name: Capillograph) with a barrel diameter of 9.55 mm, a length (L) of 8 mm, a diameter (D) of 2.095 mm, and an inflow angle of 90 °. A die was mounted and measured. For MS, the temperature was set to 190 ° C., the piston lowering speed was set to 10 mm / min, the stretch ratio was set to 47, and the load (mN) required for take-up was MS.

~ Charpy impact strength ~
The Charpy impact strength was measured according to JIS K6922-2 (1997).

~ Environmental stress cracking ~
The environmental stress crack resistance conformed to JIS K6922-2 (1997). Using a thermostat at 50 ± 0.5 ° C., the time until cracking of 10 samples was measured in a 10 wt% solution of Nonion NS210, and the F50 value was calculated.

~Surface roughness~
A capillary viscometer (Toyo Seiki Seisakusho, trade name: Capillograph) with a barrel diameter of 9.55 mm is attached to a die with a length (L) of 8 mm, a diameter (D) of 2.095 mm, and an inflow angle of 90 °. Are extruded at 190 ° C. and a shear rate of 50 s ⁻¹ . The surface roughness Ra value of the extruded strand was measured using a digital microscope (Ultra Deep Shape Measuring Microscope VK-8550 manufactured by Keyence Corporation) in accordance with JIS B0601.

~ash~
The crucible containing the sample is heated red on the burner to burn the polymer, and then heated in an electric furnace to completely ash until the weight of the crucible reaches a constant weight. After cooling the crucible in a desiccator, the amount of ash is determined from the weight difference between the crucible before and after ashing.

~ Continuous extrusion blow molding of 100L container and its evaluation ~
Using a blow molding machine (manufactured by Nippon Steel Works) having an extrusion screw of 115 mmφ, the parison is continuously extruded from the tip of the die at a cylinder temperature of 220 to 230 ° C. and a screw rotation speed of 30 rotations, with an average wall thickness of 4 mm and a container volume of 100 liters. The drum was molded, and the visual evaluation of the skin of the molded product, the visual evaluation of the pinch shape, and the drop strength were measured.

~ Accumulation blow molding of 100L container and its evaluation ~
Using a blow molding machine (manufactured by Nippon Steel) with an extrusion screw of 115 mmφ, melt resin was filled into the accumulator at a cylinder temperature of 220 to 230 ° C. and a screw rotation speed of 30 revolutions, and the parison extruded for 5 seconds was the average meat The drum was molded into a drum having a thickness of 4 mm and a container volume of 100 liters, and the visual evaluation of the skin of the molded product, the visual evaluation of the pinch shape, and the drop strength were measured.

~ Product skin ~
The surface of the container obtained by the above molding was visually observed, and a smooth skin state was marked with ◯, and a shark skin with vigorous appearance was marked with ×.

~ Pinch part shape ~
A container having a minimum thickness of 3 mm or more in the pinch portion of the container obtained by the above molding was evaluated as ◯, and less than 3 mm was evaluated as x.

~ Drop strength ~
The 100 L container obtained by the above molding was filled up with water and sealed up, and then dropped vertically from a height of 1 to 3 m with the bottom of the container down, and a drop test of three containers was performed. The case where no crack was observed by visual observation was marked with ○, and the case where crack was generated even with one container was marked with ×.

-Measurement of the number of fine particles-
Using a blow molding machine (made by Placo) having an extrusion screw of 65 mmφ, a container with a cylinder volume of 500 ml is molded at a cylinder temperature of 200 ° C., and washed in a clean room by shaking with 250 ml of ultrapure water for 15 seconds. After repeating 5 times, 250 milliliters of ultrapure water was put in the container and allowed to stand for one week, and the number of fine particles of 0.1 μm or more was measured with a KL-25 type liquid fine particle counter manufactured by Lyon Co., Ltd. 100 or less was regarded as acceptable.

Example 1
(I) HLMFR 2.5 g / 10 min, high density polyethylene manufactured using a Ziegler catalyst with a density of 955 kg / m ³ (trade name Nipolon Hard 9D03E, manufactured by Tosoh Corporation) 99.98% by weight, (II) fluoropolymer As a hydrotalcite (trade name: DHT4A, Kyowa Chemical Co., Ltd.) with 100 parts by weight of a polymer comprising 0.02% by weight of vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (trade name Dynamer FX5911X, manufactured by Sumitomo 3M Limited) A composition was obtained by melting and kneading 0.005 part by weight of Kogyo Co., Ltd. and cutting. A large container having a diameter of 440 mmφ, a height of 800 mm, an average wall thickness of 4 mm, an internal volume of 100 liters, and a container weight of 7 kg was prepared from the obtained composition using a continuous extrusion large blow molding machine. Observation of the product skin of the obtained large container and a drop test were performed. The results are shown in Tables 4 to 5. The product skin was good and passed the drop test at 3.0 m.

Example 2
(I) HLMFR 2.5 g / 10 min, high density polyethylene (trade name: Nipolon Hard 9D03E, manufactured by Tosoh Corporation) manufactured using a Ziegler catalyst having a density of 955 kg / m ³ , (II) Fluoropolymer A container was molded in the same manner as in Example 1 except that the vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (trade name Dynamer FX5911X, manufactured by Sumitomo 3M Limited) was changed to 0.05% by weight. And evaluated. The product skin was good and passed the drop test at 3.0 m.
Example 3
(I) HLMFR 2.5 g / 10 min, high density polyethylene manufactured using a Ziegler catalyst with a density of 955 kg / m ³ (trade name Nipolon Hard 9D03E, manufactured by Tosoh Corporation) 99.98% by weight, (II) fluoropolymer As a hydrotalcite (trade name: DHT4A, Kyowa Chemical Co., Ltd.) with 100 parts by weight of a polymer comprising 0.02% by weight of vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (trade name Dynamer FX5911X, manufactured by Sumitomo 3M Limited) A composition was obtained by melting and kneading 0.005 part by weight of Kogyo Co., Ltd. and cutting. A large container having a diameter of 440 mmφ, a height of 800 mm, an average wall thickness of 4 mm, an internal volume of 100 liters, and a container weight of 7 kg was produced from the obtained composition using an accumulator-type large blow molding machine. Observation of the product skin of the obtained large container and a drop test were performed. The results are shown in Tables 4 to 5. The product skin was good and passed the drop test at 3.0 m.

Example 4
(I) HLMFR 4.5 g / 10 min, high density polyethylene manufactured using a Ziegler catalyst having a density of 951 kg / m ³ (trade name: Nipolon Hard 9D03G, manufactured by Tosoh Corporation) 99.98% by weight, (II) fluoropolymer As a hydrotalcite (trade name: DHT4A, Kyowa Chemical Co., Ltd.) with 100 parts by weight of a polymer comprising 0.02% by weight of vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (trade name Dynamer FX5911X, manufactured by Sumitomo 3M Limited) A composition was obtained by melting and kneading 0.005 part by weight of Kogyo Co., Ltd. and cutting. A large container having a diameter of 440 mmφ, a height of 800 mm, an average wall thickness of 4 mm, an internal volume of 100 liters, and a container weight of 7 kg was prepared from the obtained composition using a continuous extrusion large blow molding machine. Observation of the product skin of the obtained large container and a drop test were performed. The results are shown in Tables 4 to 5. The product skin was good and passed the drop test at 3.0 m.

Comparative Example 1
(I) 0.15 parts by weight of calcium stearate is added to 100 parts by weight of high density polyethylene (trade name Nipolon Hard 9D03E, manufactured by Tosoh Corporation) manufactured using a Ziegler catalyst having a HLMFR of 2.5 g / 10 min and a density of 955 kg / m ^3. After melt-kneading, cutting was performed to obtain a composition. A container was molded from the obtained composition in the same manner as in Example 1 and evaluated. There were many fine particles, the skin was rough, the pinch shape was poor, cracks occurred in the drop test, and it was judged difficult to use as a container.

Comparative Example 2
(I) HLMFR 2.5 g / 10 min, high density polyethylene manufactured using a Ziegler catalyst with a density of 955 kg / m ³ (trade name Nipolon Hard 9D03E, manufactured by Tosoh Corporation) 99.98% by weight, (II) fluoropolymer As a hydrotalcite (trade name DHT4A, Kyowa Chemical Industry Co., Ltd.) with 100 parts by weight of a polymer comprising 0.05% by weight of vinylidene fluoride / hexafluoropropylene copolymer (trade name Dynamer FX6913, manufactured by Sumitomo 3M Co., Ltd.) (Product made) 0.005 part by weight was melt-kneaded and then cut to obtain a composition. A container was molded from the obtained composition in the same manner as in Example 1 and evaluated. The product skin was good and passed the drop test at 3.0 m, but the amount of ash was greatly increased and the amount of fine particles increased.

Comparative Example 3
(I) HLMFR 8.0 g / 10 min, density 957 kg / m ³ using a Ziegler catalyst with high density polyethylene (trade name Nipolon Hard 8D01A, manufactured by Tosoh Corporation) 100 parts by weight hydrotalcite (trade name DHT4A, A composition was obtained by melting and kneading 0.005 part by weight of Kyowa Chemical Industry Co., Ltd. and cutting. A container was molded from the obtained composition in the same manner as in Example 1 and evaluated. Although the product skin was good, it was judged that cracking occurred in a drop test at 2.0 m and it was difficult to use as a container.

Comparative Example 4
(I) 0.15 parts by weight of calcium stearate is added to 100 parts by weight of high density polyethylene (trade name Nipolon Hard 9D03E, manufactured by Tosoh Corporation) manufactured using a Ziegler catalyst having a HLMFR of 2.5 g / 10 min and a density of 955 kg / m ^3. After melt-kneading, cutting was performed to obtain a composition. A container was molded from the obtained composition in the same manner as in Example 3, and evaluated. There were many fine particles, the skin was rough, the pinch shape was poor, cracks occurred in the drop test, and it was judged difficult to use as a container.

Comparative Example 5
(I) HLMFR 3.0 g / 10 min, high density polyethylene (trade name: Novatec HB314R, manufactured by Nippon Polyethylene Co., Ltd.) manufactured using a Phillips catalyst with a density of 954 kg / m ³ is used in the same manner as in Example 1. Molded and evaluated. The product skin was good and passed the drop test at 3.0 m, but the amount of ash increased significantly and the amount of fine particles increased.

Claims (6)

It consists of 99.80 to 99.99% by weight of a polyethylene resin manufactured using a Ziegler polymerization catalyst and 0.01 to 0.2% by weight of a fluoropolymer, and satisfies the following requirements (a) to (h). A polyethylene resin composition comprising 0.005 parts by weight or more and 0.01 parts by weight or less of hydrotalcite with respect to 100 parts by weight of the total amount of polyethylene resin and fluoropolymer.
(A) Based on JIS K6922-1 (1997), the density measured by a density gradient tube method is 940 to 970 kg / m ³ ,
(B) Under the conditions of 190 ° C. and 21.6 kg load, the melt flow rate in accordance with JIS K7210 (1999) is 1 to 15 g / 10 min.
(C) The weight average molecular weight / number average molecular weight determined as a linear polyethylene equivalent value from gel permeation chromatography is 6 to 15,
(D) Using a die having a length / diameter = 8 mm / 2.095 mm, the melt tension measured under the measurement conditions of 190 ° C., piston lowering speed 10 mm / min, draw ratio 47 is 150 to 600 mN,
(E) Charpy impact strength measured according to JIS K6922-2 (1997) is 50 kJ / m ² or more,
(F) Environmental stress cracking measured in accordance with JIS K6922-2 (1997) is 100 hours or more,
(G) Surface roughness when measuring the surface of a strand extruded under the conditions of 190 ° C. and a shear rate of 50 s ⁻¹ according to JIS B0601 using a die of length / diameter = 8 mm / 2.095 mm. 5 μm or less,
(H) Ash content is 80ppm or less 2. The polyethylene resin composition according to claim 1, wherein the fluorine polymer is a vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer. A blow container comprising the polyethylene resin composition according to claim 1. The blow container according to claim 3, wherein the blow container is a large container having an internal volume of 50 liters or more. The blow container according to claim 3 or 4, wherein the blow container is a high-purity chemical container. The blow container according to any one of claims 3 to 5, wherein the blow container is continuously formed by a continuous extrusion blow molding machine.