JP2009149008A - Single-layer blow-molded product and method for producing the same - Google Patents

Abstract

An object of the present invention is to provide a high-quality single-layer blow-molded article excellent in transparency of a container and having excellent resilience, impact resistance, flexibility, and environmental stress crack resistance, and a method for producing the same.
The present invention provides a single-layer blow molded article made of polyethylene produced by a metallocene catalyst having the following characteristics (i) to (iv).
Characteristic (i): Melt flow rate (temperature 190 ° C., load 2.16 kg) is 0.5 to 28 g / 10 min.
Characteristic (ii): The density is 0.850 to 0.915 g / cm ³ .
Characteristic (iii): Flexural modulus is 170 MPs or less.
Characteristic (iv): The ratio (Mw / Mn) of the weight average molecular weight and the number average molecular weight as measured by gel permeation chromatography (GPC) is 1.5 to 4.0.
[Selection figure] None

Description

  The present invention relates to a single-layer blow-molded product and a method for producing the same, and more specifically, has a high-class feeling that is excellent in transparency of the molded product and is excellent in resilience, impact resistance, flexibility, and environmental stress crack resistance. The present invention relates to a single-layer blow molded article, particularly a hollow container, and a method for producing the same.

  Conventionally, plastic hollow molded products have been widely used in the field of containers such as shampoos, rinses, cosmetics, and medical use. Resins such as polyethylene, polypropylene, and polyethylene terephthalate are widely used as plastics for hollow molded articles. Among them, polyethylene and polypropylene are used as preferable from the viewpoint of performance, price, and the like, and many materials and molded articles with improved transparency have been proposed (for example, see Patent Documents 1 to 11).

Among them, for example, in Patent Document 1 (Japanese Patent Laid-Open No. 07-125538), an MFR produced using a metallocene catalyst is 0.1 to 50 g / 10 min, a density is 0.915 g / cm ³ or less, Ethylene and carbon having properties of HAZE of 30% or less, flexural modulus (flexibility) of ASTM D747 of 2500 kg / cm ² or less, and residue of Japanese Pharmacopoeia ignition residue test method of 0.1% by weight or less Disclosed is a medical or food liquid container made of a copolymer with α-olefin of several 4 or more, and the container is transparent, heat seal strength, heat resistance, cold resistance, low temperature, flexibility at room temperature, It is also shown that it is excellent in impact resistance, flex resistance and the like.
However, the above publication does not necessarily clearly disclose what is suitable as a highly transparent and flexible blow-molded product.

Patent Document 2 (Japanese Patent Application Laid-Open No. 09-216915) discloses polyethylene for blow molding having a specific density, melt flow rate, melt flow rate ratio, molecular weight distribution, swell ratio, preform moldability, It has been shown that a blow molding polyethylene is provided that is excellent in shrinkage properties, stretchability, and surface smoothness.
However, the above publication does not necessarily clearly disclose what is suitable as a highly transparent and flexible blow-molded product.

Patent Document 3 (Japanese Patent Application Laid-Open No. 2000-070340) discloses that (a) MFR = 0.1 to 20 g / 10 minutes and (b) temperature rising elution fractionation (TREF) elution curve maximum peak temperature is 65. When the height of the peak is H and the width at one third of the peak is W, H / W is 2 or more, and α having 3 to 18 carbon atoms. -A medical bag mainly composed of a copolymer with olefin has been proposed, not only has good hygiene, but also has excellent flexibility and transparency, heat resistance, and pin resistance that causes problems during transportation. It has been shown that a medical bag for containing a chemical solution, blood, etc., which has a good hall property is provided.
However, the above publication does not necessarily clearly disclose what is suitable as a highly transparent and flexible blow-molded product.

Patent Document 4 (Japanese Patent Laid-Open No. 2000-355045) discloses polyethylene having a melt flow rate of 4 g / 10 min or less obtained by copolymerizing ethylene and high α-olefin with a metallocene catalyst, and metallocene. At least 1 composition containing 98: 2 to 60:40 weight ratio of polyethylene having a melt flow rate of 10 g / 10 min or more obtained by copolymerizing ethylene and high α-olefin with a system catalyst A hollow molded article formed by blow molding a parison having a layer has been proposed.
However, in the case of this container, since the resin used for the surface layer is a composition composed of two types of polyethylene having different melt flow rates polymerized using a metallocene catalyst, the resulting molecular weight distribution is large, It is not always possible to obtain a molded article that is satisfactory in terms of gloss and transparency.

Further, Patent Document 5 (Japanese Patent Laid-Open No. 2000-313778) discloses propylene / α-olefin copolymer (comonomer 2% by weight or more, MFR 5-50 g / 10 min), or ethylene / α using a metallocene catalyst. -Wavelength 2 when an injection-molded sheet having a thickness of 2 mm is mainly composed of a polyolefin resin such as an olefin copolymer (comonomer 6% by weight or more, density 0.900 g / cm ³ or less, MFR 5 to 50 g / 10 min). A molded article such as a container has been proposed using a resin material having an infrared transmittance of 25% or more at .86 μm for cold parison biaxial stretch blow molding.

Patent Document 6 (Japanese Patent Laid-Open No. 2000-313053) discloses that a preform is molded by injection molding using a polyolefin-based resin material, cooled, and then the obtained preform is heated and then biaxially stretched. In the cold parison biaxial stretch blow molding method by blow molding, a method for heating a preform using an infrared lamp heater having an infrared radiation peak wavelength of 3 μm or more has been proposed.
However, these molded products and molding methods mainly use a polypropylene resin, and it cannot be said that the production of highly transparent and flexible blow molded products with a polyethylene resin is necessarily clearly disclosed. .

  Under these circumstances, the problems of conventional hollow containers made of polyethylene resin are solved, and the container has excellent transparency, excellent resilience, impact resistance, flexibility, and environmental stress crack resistance. There was a need to develop a plastic molded product.

Japanese Patent Application Laid-Open No. 07-125738 JP 09-216915 A JP 2000-070340 A JP 2000-355045 A JP 2000-313778 A JP 2000-313053 A

  In view of the above-mentioned problems of the prior art, the present invention is a high-quality plastic molded article excellent in transparency of a container and excellent in resilience, impact resistance, flexibility, and environmental stress crack resistance, that is, transparent. It is a molded product that is flexible, flexible, and has a resilience that can be restored to its original state even when the container is crushed. It is an object of the present invention to provide a molded product that is excellent in terms of soft touch and touch, has excellent physical properties such as drop impact strength, and does not cause problems such as whitening when deformed by external force applied to the container.

  As a result of intensive studies to solve the above problems, the present inventors tried blow molding using polyethylene produced with a metallocene catalyst having specific characteristics. The inventors have found that a blow molded product can be obtained, and have completed the present invention.

That is, according to the first aspect of the present invention, there is provided a single-layer blow molded article made of polyethylene produced by a metallocene catalyst having the following characteristics (i) to (iv).
Characteristic (i): Melt flow rate (temperature 190 ° C., load 2.16 kg) is 0.5 to 28 g / 10 min.
Characteristic (ii): The density is 0.850 to 0.915 g / cm ³ .
Characteristic (iii): Flexural modulus is 170 MPs or less.
Characteristic (iv): The ratio (Mw / Mn) of the weight average molecular weight and the number average molecular weight as measured by gel permeation chromatography (GPC) is 1.5 to 4.0.

  According to a second aspect of the present invention, there is provided a single-layer blow molded product characterized in that, in the first invention, the thickness of the molded product is 20 μm or more.

  Further, according to a third aspect of the present invention, in the first or second aspect of the invention, the molded article body has a haze of less than 10% and a total light transmittance of 85% or more. A molded article is provided.

  According to the fourth aspect of the present invention, in any one of the first to third aspects of the invention, the molded product is subjected to stress until the inner surfaces thereof are in contact with each other at the center of the cylinder, and then is removed for 5 seconds after the stress is removed. A single-layer blow-molded product is provided that is restored to its original shape within the original range.

  Further, according to a fifth aspect of the present invention, there is provided a single-layer blow molded product according to any one of the first to fourth aspects, wherein the polyethylene contains 1000 ppm or less of a lubricant.

Further, according to the sixth aspect of the present invention, a mold having a mold cavity surface with a surface roughness of 0.1 to 0.9 μm is blown under a blow molding pressure of 0.05 to 0.8 MPa. A method for producing a single-layer blow-molded article according to any one of the first to fifth inventions is provided.
Furthermore, according to the seventh aspect of the present invention, in the sixth aspect, the ratio (T1 / T2) of the time (T1) for the parison length to reach 60 cm and the time (T2) for the length of 12 cm to reach 12 cm is 2 or more. A method for producing a single-layer blow-molded product is provided, which is blow-molded under the following conditions.

  According to the present invention, a high-quality plastic that adopts polyethylene having specific physical properties and is excellent in transparency, and has excellent resilience, impact resistance, flexibility, and environmental stress crack resistance by blow molding of a specific material. A molded product is obtained. In addition, because it has a container shape, it is excellent in handleability, flexibility, soft touch, touch, drop impact strength, etc. during molding, and does not cause problems such as whitening when deformed due to external force applied The industrial utility is very high.

The present invention is a single-layer blow-molded article made of polyethylene produced by a metallocene catalyst having the following characteristics (i) to (iv), and a production method thereof.
Characteristic (i): Melt flow rate (temperature 190 ° C., load 2.16 kg) is 0.5 to 28 g / 10 min.
Characteristic (ii): The density is 0.850 to 0.915 g / cm ³ .
Characteristic (iii): Flexural modulus is 170 MPs or less.
Characteristic (iv): The ratio (Mw / Mn) of the weight average molecular weight and the number average molecular weight as measured by gel permeation chromatography (GPC) is 1.5 to 4.0.
Hereinafter, materials and characteristics for forming the single-layer blow molded article of the present invention, a molding method thereof, and the like will be described in detail.

[I] Material and Characteristics of Blow Molded Product The blow molded product of the present invention is a single-layer blow molded product, and is molded using polyethylene produced with a metallocene catalyst.
The polyethylene used as the blow molded product has a melt flow rate (MFR) of 0.5 to 28 g / 10 min, preferably 1.0 to 25 g / 10 at a temperature of 190 ° C. and a load of 2.16 kg in accordance with JIS K6922-2: 1997. Minutes.
When the MFR of the polyethylene of the present invention is less than 0.5 g / 10 minutes, the surface of the molded product tends to be rough. On the other hand, if the MFR exceeds 28 g / 10 min, in the case of stretch blow molding, a) the mold releasability at the time of injection molding deteriorates, b) the surface of the molded preform becomes rough, c) stretching There is a tendency that the stretchability in the process is deteriorated and it is difficult to obtain a uniform thick container, d) the air release in the mold cavity is deteriorated, and the unevenness pattern is generated in the molded container. In the case of direct blow molding, a) the surface of the extruded parison tends to be sticky, which may cause the tip of the die to become dirty, or foreign matter may easily adhere to the surface, b) air in the mold cavity There is a tendency for the punching to worsen and the unevenness of the molded container to occur, c) to draw down, etc. These tendencies begin to appear at over 8.0 g / min in direct blow molding.
The MFR of polyethylene can be adjusted by changing the amount of hydrogen coexisting during ethylene polymerization, changing the polymerization temperature, etc., and increasing the amount of hydrogen or increasing the polymerization temperature. Can do.

The polyethylene used as the blow molded product has a density measured according to JIS K6922-1 and 2: 1997 of 0.850 to 0.915 g / cm ³ , preferably 0.870 to 0.912 g / cm ³ . in the density is less than 0.850 g / cm ³ tends to decrease the heat resistance of the molded containers, exceeds 0.915 g / cm ^3, air vent of the crystallization rate is fast becomes mold cavity surface is difficult As a result, irregularities are likely to occur on the surface of the molded product. Moreover, there exists a tendency for transparency to be inferior.
The density of the polyethylene can be adjusted by changing the amount of α-olefin copolymerized with ethylene, and can be decreased by increasing the amount of α-olefin.

Polyethylene used as a blow molded product has a flexural modulus measured in accordance with JIS K6922-2 of 170 MPs or less, and preferably 150 MPs or less. When the flexural modulus exceeds 170 MPa, the flexibility tends to decrease. Although a lower limit is not specifically limited, If it is 10 Mpa or less, the intensity | strength as a container will fall and it is not practical.
The flexural modulus can be adjusted by adjusting the density of polyethylene, and can be increased by increasing the density.

The polyethylene used as the blow molded product has a weight average molecular weight to number average molecular weight ratio (Mw / Mn) of 1.5 to 4.0, preferably 2.0 to 3.5, as determined by gel permeation chromatography (GPC). More preferably, it is 2.5-3.3. If Mw / Mn by GPC measurement is less than 1.5, melt fracture is likely to occur in the parison, and if it exceeds 4.0, the surface skin of the parison tends to be finely roughened.
Mw / Mn by GPC measurement can be increased or decreased by adjusting the mixing ratio of the high molecular weight component and the low molecular weight component, and the polymer having different molecular weight by changing the polymerization temperature or the amount of chain transfer agent during the polymerization reaction. Components are formed, and as a result, the molecular weight distribution of the entire polymer can be changed. It is also possible to increase or decrease the molecular weight distribution by performing polymerization with different polymerization conditions in multiple stages.

Gel permeation chromatography (GPC) measurement conditions and measurement methods, and molecular weight calculation methods are as follows.
Use (i) Measurement Conditions c _o Tazu Inc. Model 150C, subjected to GPC measurement under the following conditions to determine the weight average molecular weight (Mw).
Column: Shodex HT-G (manufactured by Showa Denko KK) and HT-806M (manufactured by Showa Denko KK) x 2 Solvent: 1,2,4-trichlorobenzene Temperature: 140 ° C.
Flow rate: 1.0 ml / min Injection volume: 300 μl
(Ii) Sample preparation Approximately 3 mg of a sample and 3.0 ml of a solvent were weighed into a commercially available 4 ml screw top vial, and shaken at a temperature of 150 ° C. for 2 hours using an SSC-9300 type stirrer manufactured by Senshu Kagaku.
(Iii) Calculation of molecular weight GPC chromatographic data is loaded into a computer at a frequency of 1 point / second, processed according to the description in Chapter 4 of “Size Exclusion Chromatography” published by Sadao Mori and Kyoritsu Shuppan Co., Ltd. The value was calculated.
(Iv) Column calibration Monolithic polystyrene (S-7300, S-3900, S-1950, S-1460, S-1010, S-565, S-152, S, manufactured by Showa Denko K.K.) -66.0, S-28.5, S-5.05), each 0.2 mg / l solution of n-eicosane and n-tetracontane, a series of monodisperse polystyrene measurements were taken and their A calibration curve was obtained by fitting the relationship between the elution peak time and the logarithm of molecular weight with a quartic polynomial.
In addition, the molecular weight of polystyrene was converted into the molecular weight of polyethylene using the following formula.
M _PE = 0.468 × M _PS

  The thickness of the molding container in the blow molded product of the present invention is preferably 20 μm or more, more preferably 100 to 800 μm. If thickness is less than 20 micrometers, the handleability of a container will fall. The thickness is adjusted by adjusting the die / core distance of the hollow molding machine.

The body of the blow-molded product of the present invention preferably has a haze measured in accordance with JIS-K7105: 1981 of less than 10% and a total light transmittance of 85% or more, more preferably a haze of 7 % Or less, and the total light transmittance is 90% or more. If the haze is out of the above range, the transparency tends to be inferior and the sense of quality is impaired.
The haze is affected by the density of the resin used, and the haze can be reduced as the density is lower. The total light transmittance is influenced by the density of the resin used, and can be increased as the density is lower.

The blow-molded product of the present invention is preferably one in which stress is applied to the inner surface of the cylinder until the inner surfaces come into contact with each other, and then the original shape is restored within 5 seconds after the stress is removed. Unless it is restored to its original shape for more than 5 seconds, it becomes impractical as a flexible container.
In order to achieve the restorability of the molded product, an area having a low density under the influence of the density to be used can exhibit an appropriate restorability.

  The polyethylene of the present invention is obtained by homopolymerization of ethylene, or ethylene and an α-olefin having 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1- Obtained by copolymerization with octene or the like. Also, copolymerization with a diene for the purpose of modification is possible. Examples of the diene compound used at this time include butadiene, 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene, and the like. The comonomer content during the polymerization can be arbitrarily selected. For example, in the case of copolymerization of ethylene and an α-olefin having 3 to 12 carbon atoms, an ethylene / α-olefin copolymer is used. The α-olefin content therein is 0 to 40 mol%, preferably 0 to 30 mol%.

As the polyethylene polymerization catalyst used in the present invention, various catalysts such as a Ziegler catalyst, a Phillips catalyst, and a metallocene catalyst are used. Preferably, a metallocene catalyst is used. A metallocene catalyst is a type of catalyst called a single-site catalyst that has a relatively single active site, and is typically a transition metal metallocene complex, such as a biscyclopentadienyl complex of zirconium or titanium. A catalyst obtained by reacting methylaluminoxane or the like as a cocatalyst can be mentioned, and it is a homogeneous or heterogeneous catalyst in which various complexes, cocatalysts, carriers and the like are variously combined.
Examples of the metallocene catalyst include JP-A-58-19309, 59-95292, 59-23011, 60-35006, 60-35007, 60-35008, and 60-35009. No. 61-130314 and JP-A-3-163088, and the like.

The polyethylene of the present invention can be produced by a production process such as a gas phase polymerization method, a solution polymerization method, a slurry polymerization method, or a high pressure polymerization method. Among the polymerization conditions of the ethylene polymer, the polymerization temperature can be selected from the range of 0 to 300 ° C. The polymerization pressure can be selected from the range of atmospheric pressure to about 100 kg / cm ² . It is selected from aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as benzene, toluene and xylene, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, etc. in a state where oxygen and water are substantially cut off. It can be produced by polymerizing ethylene and α-olefin in the presence of an inert hydrocarbon solvent.

In the above polymerization, hydrogen supplied to the polymerization vessel is consumed as a chain transfer agent, determines the average molecular weight of the produced ethylene-based polymer, and partly dissolves in a solvent and is discharged from the polymerization vessel. The solubility of hydrogen in the solvent is small, and the hydrogen concentration near the polymerization active point of the catalyst is low unless a large amount of gas phase is present in the polymerization vessel. Therefore, if the hydrogen supply amount is changed, the hydrogen concentration at the polymerization active point of the catalyst changes rapidly, and the molecular weight of the produced ethylene polymer changes following the hydrogen supply amount in a short time. Therefore, a more homogeneous product can be produced by changing the hydrogen supply rate in a short cycle. Moreover, the aspect of changing the hydrogen supply amount is preferably changed discontinuously rather than continuously because the effect of broadening the molecular weight distribution can be obtained.
In the ethylene polymer according to the present invention, it is important to change the hydrogen supply amount, but other polymerization conditions such as polymerization temperature, catalyst supply amount, supply amount of olefin such as ethylene, 1-butene It is also important to change the supply amount of the comonomer and the like, the supply amount of the solvent, etc., simultaneously with the change of hydrogen or separately.

  The ethylene polymer produced by the above method can be pelletized by mechanical melt mixing with a pelletizer or homogenizer according to a conventional method, and then molded by various molding machines to obtain a desired molded product. . In addition to the other olefin polymers and rubbers, etc., the ethylene polymer obtained by the above-mentioned method is not limited to antioxidants, ultraviolet absorbers, light stabilizers, lubricants, antistatic agents, Clouding agent, anti-blocking agent, processing aid, color pigment, pearl pigment, glittering material, polarizing pearl pigment, crosslinking agent, foaming agent, neutralizing agent, heat stabilizer, crystal nucleating agent, inorganic or organic filler, flame retardant A known additive such as can be blended. As a coloring method, a compound added in a necessary amount to the base resin or a master batch added at a high concentration may be post-blended.

As additives, for example, antioxidants (phenolic, phosphorus-based, sulfur-based), lubricants, antistatic agents, light stabilizers, ultraviolet absorbers, and the like can be appropriately used in combination of one or more. As the filler, calcium carbonate, talc, metal powder (aluminum, copper, iron, lead, etc.), silica, diatomaceous earth, alumina, gypsum, mica, clay, asbestos, graphite, carbon black, titanium oxide, etc. can be used. . In any case, various additives may be blended with the ethylene polymer as necessary, and the mixture may be kneaded with a kneading extruder, a Banbury mixer, or the like to obtain a molding material.
When the blow molded product of the present invention contains a lubricant of 1000 ppm or less, the gloss of the molded product surface is further improved. As the lubricant, a fatty acid amide compound is preferable. Of these, erucic acid amide is preferred. When the amount of the lubricant is 300 to 1000 ppm with respect to polyethylene, the slipping property between the molded preform and the mold is improved, and as a result, a preform without deformation can be molded, which has an adverse effect on the stretch blow process. Disappears. If the addition amount is 300 ppm or less, the effect is low, and if it exceeds 1000 ppm, a tendency to bleed out on the surface or inner surface of the molded product appears.

[II] Blow container and production method thereof The blow molded product of the present invention can be produced using a normal direct blow molding machine and a stretch blow molding machine. The molding conditions can be appropriately set depending on the size and shape of the molded product to be obtained. However, the layer configuration is not necessarily limited to the thickness of the laminate, but the thickness is preferably 20 to 1500 μm, more preferably 100. ˜800 μm.
In addition, burrs and the like generated by direct blow molding may be crushed and blended with a base resin.

  The container of the present invention may be decorated with screen printing, in-mold labels in which a label is inserted into a mold at the time of blow molding, or decoration with a shrink film or a stretch film.

  As the cooling mold used for the production of the blow molded article of the present invention, a mold during normal blow molding can be used. The cavity surface of the mold is sandblasted, and is applied to remove the air existing between the mold cavity and the parison when the parison is sandwiched between the mold cavity surface and the parison is inflated with an air pin. There are many.

In the case of direct blow molding, the cavity surface of the molding die has a blast finish with a surface roughness Ra value measured in accordance with JIS-B0601: 1982 in the range of 0.2 to 0.9 μm. A container having a smooth surface can be obtained by molding with each mold. If the surface roughness Ra value of the mold cavity surface exceeds 0.9 μm, the mold cavity surface is transferred, and the surface of the molded container is reduced in smoothness. On the other hand, when the surface roughness Ra value is less than 0.2 μm, air bleeding is poor and a non-uniform pattern is generated on the surface of the molded container.
Specifically, the surface of the container has a uniform appearance by roughening the mold surface roughness of the shoulder R (shoulder radius) and bottom R (bottom radius) of the container and making the barrel finer. Can be obtained. Further, by adjusting the blow pressure in the range of 0.05 to 0.8 MPa and forming, it is possible to form without generating a fluttering uneven pattern. That is, by first performing blow molding at a low pressure and then molding by increasing the pressure, it is possible to obtain a good container having no fluttering pattern.

In the case of stretch blow molding, the mold cavity surface can be molded with a mold having a blast finish of 0.1 to 0.3 μm to obtain a container having a smooth surface. I can do it. When the surface roughness Ra value of the mold cavity surface exceeds 0.3 μm, the mold cavity surface is transferred, and the surface of the molded container is reduced in smoothness. On the other hand, if the surface roughness Ra value is less than 0.1 μm, air bleeding is poor and a non-uniform pattern is generated on the surface of the molded container.
Specifically, the surface of the container has a uniform appearance by roughening the mold surface roughness of the shoulder R (shoulder radius) and bottom R (bottom radius) of the container and making the barrel finer. Can be obtained. Further, by adjusting the blow pressure in the range of 0.05 to 0.8 MPa and forming, it is possible to form without generating a fluttering uneven pattern. That is, after blow molding is first performed at a low pressure, a good container having no fluttering pattern can be obtained by molding at a higher pressure.

The blow molded product of the present invention can be made into a blow molded product by a blow molding method, particularly a direct blow molding machine, a rotary blow molding machine, a hot parison stretch blow molding machine or the like. Further, a cold parison stretch blow molding machine or injection blow molding is also possible.
The molding pressure in blow molding is preferably 0.05 to 0.8 MPa. When the molding is performed within the range, a molded product having a good surface gloss can be molded.
In blow molding, it is preferable that the ratio (T1 / T2) of the time (T1) for the parison length to reach 60 cm and the time (T2) for reaching 12 cm is 2 or more. Within this range, a molded article having a better appearance can be obtained.

  The size of the blow molded product is not particularly limited, but is preferably about 10 to 2000 ml. Further, the shape of the container is not particularly limited. The resulting blow-molded product is transparent, and is a high-grade plastic molded product with excellent resilience, impact resistance, flexibility, and environmental stress crack resistance. , Shampoo, rinse, cosmetics, medical, etc.Excellent in physical properties, soft touch, soft touch, etc., excellent in handling properties, drop impact strength, etc. It can be suitably used as a container for food, a container for food such as edible oil, etc., and its industrial utility is very high.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples unless it exceeds the gist. The measurement methods and materials used in the examples are as follows.

[1] Measuring method (1) Melt flow rate (MFR): Measured according to JIS K6922-2: 1997 at a temperature of 190 ° C. and a load of 2.16 kg.
(2) Density: Measured according to JIS K6922-1 and 2: 1997.
(3) Flexural modulus: measured in accordance with JIS K6922-2.
(4) GPC: Measurement conditions and measurement method, and molecular weight calculation method were performed as follows.
Use (i) Measurement Conditions c _o Tazu Inc. Model 150C, subjected to GPC measurement under the following conditions to determine the weight average molecular weight (Mw).
Column: Shodex HT-G (manufactured by Showa Denko KK) and HT-806M (manufactured by Showa Denko KK) x 2 Solvent: 1,2,4-trichlorobenzene Temperature: 140 ° C.
Flow rate: 1.0 ml / min Injection volume: 300 μl
(Ii) Sample preparation Approximately 3 mg of a sample and 3.0 ml of a solvent were weighed into a commercially available 4 ml screw top vial, and shaken at a temperature of 150 ° C. for 2 hours using an SSC-9300 type stirrer manufactured by Senshu Kagaku.
(Iii) Calculation of molecular weight GPC chromatographic data is loaded into a computer at a frequency of 1 point / second, processed according to the description in Chapter 4 of “Size Exclusion Chromatography” published by Sadao Mori and Kyoritsu Shuppan Co., Ltd. The value was calculated.
(Iv) Column calibration Monolithic polystyrene (S-7300, S-3900, S-1950, S-1460, S-1010, S-565, S-152, S, manufactured by Showa Denko K.K.) -66.0, S-28.5, S-5.05), each 0.2 mg / l solution of n-eicosane and n-tetracontane, a series of monodisperse polystyrene measurements were taken and their A calibration curve was obtained by fitting the relationship between the elution peak time and the logarithm of molecular weight with a quartic polynomial.
In addition, the molecular weight of polystyrene was converted into the molecular weight of polyethylene using the following formula.
M _PE = 0.468 × M _PS

(5) Haze: Measured according to JIS K7105: 1981.
(6) Total light transmittance: measured in accordance with JIS K7105: 1981.
(7) Parison (preform) temperature: The extruded resin was measured with a rod-shaped thermocouple thermometer.
(8) Surface roughness: The surface roughness of the mold cavity surface was measured according to JIS B0601: 1982.
A mold finished with a mold cavity surface roughness of less than 0.1 μm was designated as “A”.
A mold finished with a mold cavity surface roughness of 1.0 μm was designated as “B”.
The mold cavity surface roughness was adjusted by changing the roughness of the shoulder R part and bottom R part to 0.9 μm and the body part to 0.2 μm, and the finished mold was designated as “C”.
The mold cavity surface roughness was adjusted by changing the roughness of the shoulder R portion and the bottom R portion to 0.3 μm and the barrel portion to 0.1 μm, and the finished mold was designated as “D”.
(9) Blow pressure:
“A” was blown at a blow molding pressure of 0.8 MPa.
The pressure at the time of blow molding was blown at 0.05 MPa for 1.5 seconds, and then blown at 0.8 MPa was designated as “b”.

(10) Appearance of molded product: The appearance of a container that is a blow-molded product is evaluated visually, and its state is evaluated. Or, “Skin rough” occurs when there is no uniform skin feeling, “Small occurs” when the air in the mold cavity is poorly vented, “Melt fracture” occurs in the parison, and “Parison surface is finely roughened” "Melfra generation", the one that transferred the cavity surface of the mold and lowered the transparency was called "matte".
(11) Drawdown: When the ratio (T60 / T12) of the time for the parison to reach 60 cm from the tip of the die (T60) and the time to reach 12 cm from the tip of the die (T12) (T60 / T12) is less than 2, with drawdown, 2 or more In the case of no drawdown.
(12) Parison stickiness: The extruded parison is sandwiched between molds, and the parison outside the mold is cut with a cutter. At that time, it is judged visually whether the parison pulls the yarn or not, and the yarn is pulled. “None” was assigned to the one that did not exist, and “Yes” was assigned to the one that pulled the thread.
(13) Preform releasability: “No” indicates that the preform adheres to the cavity and the core during preform molding, and “Good” indicates that the preform does not adhere.
(14) Preform stability: After preform molding, the preform immediately before stretch blow molding contracts and bends or draws down is judged as “No”, and the preform that does not bend or does not draw down is judged as “good”. .
(15) Restorability: When the center part of an empty molding container without a cap is crushed with the fingertip until the inner wall surface comes into contact with the finger, and the finger is released, the original shape is restored to 95% or more within 5 seconds. “Good” and those not restored are “No”.

[2] Resin material Direct blow resin Polyethylene (A-1) to (A-10) and polypropylene (A-11) shown in Table 1 were used.

2. Stretch blown resin Polyethylene (B-1) to (B-12), (B-5 ′) and polypropylene (B-13) shown in Table 2 were used. However, 900 ppm of erucic acid amide was added to polyethylene (B1-10).

[Example 1] (Direct blow molding)
With a φ50mm direct blow molding machine, adjust the molding resin temperature setting at the specified screw speed, extrude the parison, and change and adjust the blow mold cavity surface roughness Ra value for a 300 ml cylindrical container. The mold temperature is 20 ° C, the blow pressure at the time of blowing is changed and adjusted, and then the bottle weight is 18 g (the thickness of the container body is 0.4 to 0.7 mm) and the molding cycle is 12 seconds. I did it.
Polyethylene (A-1) was used as the resin, and blow molding was performed by adjusting the heater temperature of the extruder, head, and die so that the inner and outer skins of the parison were low, and the hollow container was obtained. Various physical properties of the obtained container are shown in Table 1.

[Examples 2 to 5] (Direct blow molding)
Blow molding was performed in the same manner as in Example 1 except that the resin shown in Table 1 was used instead of polyethylene (A-1) as a resin to obtain a hollow container. Various physical properties of the obtained container are shown in Table 1.

[Comparative Examples 1 to 9] (Direct blow molding)
Blow molding was performed in the same manner as in Example 1 except that the resin shown in Table 1 was used instead of polyethylene (A-1) as a resin to obtain a hollow container. Various physical properties of the obtained container are shown in Table 1.

[Example 6] (Stretch blow molding)
Injection resin temperature, screw rotation speed, injection pressure / flow rate, back pressure, measuring position, injection time, cooling time, blow pressure, stretching speed, preform mold temperature, product mold temperature in hot parison method stretch blow molding machine After adjusting the roughness Ra value of the cavity surface of the 600 ml cylindrical container mold, the draw ratio is 2.5 times wide, 1.2 times long, and the bottle weight is 24 g (container wall thickness 0 .4 to 0.9 mm), and molding was performed at a molding cycle of 15 seconds.
Polyethylene (B-1) was used as the resin, and the injection-molded preform did not bend and did not roughen the skin, and was subjected to stretch blow molding under conditions to obtain a hollow container. Various physical properties of the obtained container are shown in Table 2.

[Examples 7 to 12] (Stretch blow molding)
Extensive blow molding was performed in the same manner as in Example 6 except that the resin shown in Table 2 was used instead of polyethylene (B-1) as a resin to obtain a hollow container. Various physical properties of the obtained container are shown in Table 2.

[Comparative Examples 10 to 19] (Stretch blow molding)
Extensive blow molding was performed in the same manner as in Example 6 except that the resin shown in Table 2 was used instead of polyethylene (B-1) as a resin to obtain a hollow container. Various physical properties of the obtained container are shown in Table 2.

As is clear from the evaluation results of Tables 1 and 2, in Examples 1 to 12, the container which is a blow molded article of the present invention uses a specific physical property polyethylene, so that the parison can be used in direct blow molding and stretch blow molding. When forming the surface, the surface of the parison (preform) has moderate fluidity to produce a highly smooth surface skin, and the molded container has a smooth surface skin and excellent transparency. It can be seen that the container is more flexible and has a resilience.
On the other hand, in Comparative Examples 1 to 19, the obtained containers had poor performance evaluation of one or more of parison (preform) smooth surface skin, molded container surface skin, excellent transparency performance, and resilience. It turns out that it is a result.

  According to the present invention, a plastic blow molded product excellent in transparency, flexibility and impact resistance, in particular, excellent in transparency of a container, and also in resilience, impact resistance, flexibility and environmental stress crack resistance. A hollow container having an excellent luxury feeling can be provided. Since these containers can be widely used in the field of containers such as shampoos, rinses, cosmetics, and medical use, their industrial utility is very high.

Claims (7)

A single-layer blow molded article made of polyethylene produced with a metallocene catalyst having the following characteristics (i) to (iv):
Characteristic (i): Melt flow rate (temperature 190 ° C., load 2.16 kg) is 0.5 to 28 g / 10 min.
Characteristic (ii): The density is 0.850 to 0.915 g / cm ³ .
Characteristic (iii): Flexural modulus is 170 MPs or less.
Characteristic (iv): The ratio (Mw / Mn) of the weight average molecular weight and the number average molecular weight as measured by gel permeation chromatography (GPC) is 1.5 to 4.0.   The single-layer blow-molded product according to claim 1, wherein the thickness of the molded product is 20 µm or more.   The blow molded product according to claim 1 or 2, wherein the molded product body has a haze of less than 10% and a total light transmittance of 85% or more.   The molded product is restored to its original shape within 5 seconds after applying stress until the inner surfaces of the molded product are in contact with each other, and after removing the stress. Single-layer blow molded product as described.   The said polyethylene contains 1000 ppm or less of lubricants, The single layer blow molded product in any one of Claims 1-4 characterized by the above-mentioned.   Blow molding is performed under a blow molding pressure of 0.05 to 0.8 MPa using a mold having a surface roughness of a mold cavity surface of 0.1 to 0.9 µm. 6. A method for producing a single-layer blow molded article according to any one of 5 above.   The blow molding is performed under a condition that a ratio (T1 / T2) of a time (T1) for reaching a parison length of 60 cm and a time (T2) for reaching a length of 12 cm is 2 or more. Method for producing a single-layer blow molded article.